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4.0L Jeep Six: Cylinder #1 Misfire Trouble Code

Jeep Wrangler Jeep TJ Jeep inline six Jeep 4.0L Jeep how-to

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#1 jj_jeep

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Posted 08 June 2013 - 09:48 AM

My TJ has an occasional cylinder 1 misfire indicated by the check engine light and an occasional lurch at highway speed.  I have noticed the misfire when cruising at highway speed after driving about 20 minutes and feeling a sudden lurch, or when sitting at a red light idling.  The engine runs fine aside from the occasional lurch and running rough at idle.  I suspected a sticky lifter so I ran Sea Foam in the oil for about 2k miles and then changed the oil and filled with 10w-40.  I never noticed a misfire on the highway after this, but it idles rough at stop lights and the check engine light came back on at a stoplight.  It will probably turn off if I drive the highway a few times.  Wondering if there's an interim fix to get by another 6 months or year without getting stranded by this thing.  It's a 1998 with 250k miles on it, but I'm trying to put off replacing the engine due to the expense and I'm not sure it's worth it on a vehicle this "used".  Is there any chance an even heavier weight oil is a temporary fix?  Or is this engine shot and needs overhaul or replacement? 



#2 Moses Ludel

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Posted 08 June 2013 - 04:04 PM

Hi, JJ, and welcome to the forums!  The #1 misfire could be a variety of things.  Since you did ask about engine longevity and whether the engine is at the end of its duty cycle, I'll start with a suggestion:  Begin with a compression test, or better yet, a cylinder leak down test.  Any internal combustion engine needs four things to be "right", I talk about these basics in each of my books.  My mantra for basic engine condition:

 

1) Normal compression or cylinder seal, I prefer a leak down test for this reason.

2) Normal oil pressure and flow, since the bearings and lubricated parts must remain in reliable condition.

3) Normal valve timing, which means the timing chain and sprockets are in good condition.

4) Normal valve lift, which means that the camshaft lobes, lifters and rocker assemblies are in good condition.

 

Once you get past these concerns, any engine problems are either vacuum leaks, "tune" related or engine management (fuel/spark) issues. 

 

Your TJ 4.0L engine uses an ignition distributor for the high tension spark delivery alongside an MPI fuel system.  The distributor spark timing is fully controlled by the PCM (computer) and its sensor readings.  The PCM also controls fuel flow through the injectors.  A check light or 'MIL' with a consistent "#1 Cylinder Misfire" could be relative to either fuel flow or the spark at that cylinder. 

 

Spark wise, this could be a weak spark lead, worn distributor cap and rotor, the spark plug itself, or engine troubles like low compression or a leaky valve.  A misfire can also be fuel related.  Poor fuel pressure/supply can be the issue.  (See the Mopar EFI comments in the threads from the CJ forum:  Mopar EFI Conversion starving for fuel.) 

 

The injector for #1 cylinder can be clogged, too.  Or, there may be an unrelated device to consider, like the throttle position sensor (TPS) or the oxygen sensor (upstream sensor).  Sometimes, these other components will not send their own signal, yet they contribute to something like the #1 misfire.  I don't recommend replacing a number of parts randomly, JJ, I'm just calling attention to related trouble spots...

 

After ruling out the overall engine condition, I'd check the fuel pressure at the injector rail.  This should be around 49.2 PSI +/- 2 to 5 PSI.  That test can be revealing.  The #1 spark wire lead should also be tested for ohms-resistance, and spark to the #1 plug should  appear consistent. 

 

Spark plug and other ignition issues should be ruled out.  The #1 injector is more likely to be consistently faulty—not likely to be intermittently faulty.  This is still a possibility, though, so don't rule out a defective injector.

 

For additional troubleshooting guidelines, see these two articles at the magazine, covering tune and troubleshooting on Jeep MPI fuel-and-spark management like yours, JJ:

 

http://www.4wdmechan...leshooting.html

 

http://www.4wdmechan...leshooting.html

 

Let the forum community know what you turn up.  I'm certain other forum members will benefit from this exchange, JJ, your questions are thoughtful! 

 

I'm here for more discussion...

 

Moses



#3 jj_jeep

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Posted 09 June 2013 - 12:00 PM

Hi Moses,

 

Thanks for the reply.  I really appreciate your use of fundamentals when troubleshooting.  Our family has a busy summer ahead, so I'll try and post some results when I can.  Probably not for at least a couple weeks.  I need to scare up a leak down tester.  I saw a video http://www.youtube.c...h?v=GvG22YMOzUI on how to do it that looked pretty good. 

 

I suspect #1 - cylinder seal - may be a problem because of the high mileage.  I was hoping 10W40 might help extend the engine a bit here? 

I suspect #4 - valvetrain wear - may also be a problem due to high mileage. 

Based on the oil pressure gage in the instrument cluster, #2 seems OK as oil pressure runs where it has been for 15 years. 

I'll have to check past repair slips, but I think for #3 the timing chain and sprockets and water pump were replaced in the last five years. 

I hear and smell exhaust under the hood when the engine is running.  The engine used to have the standard ticking of the tappets, but now it makes a putt-putt sound like an old tractor.  I'm still running the stock header after all these years, so perhaps it is cracked or maybe the gasket between the header and head has failed?  Any reason to believe this would relate to a misfire? 

Adding to my puzzlement is the fact that this engine consumes no measureable amount of oil and has good power.  The dipstick reads full even when I'm ready for the 3k-5k oil change. 

 

Thanks again



#4 Moses Ludel

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Posted 09 June 2013 - 05:39 PM

JJ...I understand your time constraints and family commitments.  Family takes precedence...I'll respond to your questions then open a new, follow-up topic about why I recommend the use of a leak down tester compared to a compression gauge...First, your questions and my answers:

 

Q: I suspect cylinder seal may be a problem because of the high mileage.  I was hoping 10W-40 might help extend the engine life a bit here? 

A: Yes, we're attempting to rule out a cylinder seal problem.  There are two entirely different ways to look at cylinder seal: 1) adequate spinning compression to produce sufficient combustion, and 2) true cylinder seal that will prevent seepage under load and resist blow-by. 10W-40 instead of 5W-30 will not compensate much for wear; however, it will help alleviate nuisance rear main or timing cover seal seepage (will not stop an actual leak), and it may reduce oil consumption from valve guide, guide seal or ring blow-by issues.  The wear we're concerned about in terms of leak down is at the valves, rings and head gasket—and casting leaks in the worst case scenario, like a cracked cylinder head from severe overheating.

 

Q: I suspect valvetrain wear may also be a problem due to high mileage. 

A: This can be a problem, and we'll get right down to the bottom of that issue in my follow-up topic on the leak down test! If you mean valvetrain wear in terms of valve lift error, valve lift can be measured with a dial indicator at the rocker arms (valve cover removed). You do need proper valve timing and correct valve lift.  Valve lift corresponds to the camshaft lobe shape, lifter function, valve/lifter clearance and rocker arm function.

 

Q: Based on the oil pressure gauge in the instrument cluster, oil pressure runs where it has been for 15 years. 

A: This is a good sign, helpful in terms of bearing life expectancy if you do make other repairs.  If pressure did read low, you might want to make major repairs rather than spending money on a patch repair.  Avoid the proverbial "good money after bad" scenario... 

 

Q: I'll have to check past repair slips, but I think the timing chain and sprockets and water pump were replaced in the last five years. 

A: That's helpful and would eliminate or reduce the likelihood of having a valve timing problem.  Had the valve timing not been set properly, you would have experienced trouble immediately, as the PCM receives both a crankshaft position and camshaft position reading from your TJ 4.0L inline six.  If out of sync too much, the PCM would throw a trouble code.

 

Q: I hear and smell exhaust under the hood when the engine is running.  The engine used to have the standard ticking of the tappets, but now it makes a putt-putt sound like an old tractor.  I'm still running the stock header after all these years, so perhaps it is cracked or maybe the gasket between the header and head has failed?  Any reason to believe this would relate to a misfire? 

A: The sound of an exhaust leak could very well be a cracked OEM header, it's amazing that your header lasted this long if original!  Sounds like a leak from the exhaust manifold gasket area or a cracked exhaust manifold/header.  This would not be the "cause" of the misfire, however, an exhaust leak near the head is dangerous in terms of valve warp risk.  Under extreme conditions, if colder air drafts back into the engine (at the exhaust port or ports) when the engine shuts off, an exhaust valve can warp.  Valve warp like this is unlikely, and the leak down test will reveal that kind of problem.  (See my leak down tester follow-up topic post.)

 

Q: Adding to my puzzlement is the fact that this engine consumes no measureable amount of oil and has good power.  The dipstick reads full even when I'm ready for the 3k-5k oil change.

A: Let's not rule out the possibility that the engine is still viable and functions okay!  In my follow-up on the leak down test, I will explain how oil consumption does not always occur when there is engine wear.  An engine can have oil ring seal without compression ring seal; in the extreme, this can be an engine with inadequate compression or cylinder seal, yet an engine that still resists oil blow-by and oil burning—or "consumption". 

 

Keep in mind, JJ, we're simply trying to rule out an engine condition issue, separating engine "long block" problems from vacuum leaks, fuel flow issues and spark misfire.  If the basic engine tests okay, the tune-related problems can be sorted out and fixed.

 

Please see the leak down test explanation at my follow-up leak down test post...

 

Moses   



#5 jj_jeep

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Posted 16 July 2013 - 12:17 PM

Hi Moses,

 

I have a small update on my cylinder 1 misfire on my 1998 TJ with 250k miles (and counting). 

 

I stopped by the auto parts store to shop for a cylinder leak down tester.  I've read what you wrote about how to do the cylinder leak down test and I was making a list of what I'll need:

 

Leak down tester

air compressor (I only have a small tire/ball inflator)

Looks like about a 3/4" bolt to turn the crankshaft to TDC (I have basic wrenches and sockets)

A spark plug wire boot puller because the one on cylinder #1 is tough to remove because of the AC plumbing

 

More to the point, while I was there I thought it would be good to borrow their OBDII scan tool and check the recent codes just to see if any other cylinders are misfiring.  Every time I've checked it (until today), I get P0301 Cylinder 1 misfire detected. 

 

Today I got three codes - maybe this gives some more valuable clues as to why my engine is misfiring...  With the engine off, I plugged in the scan tool, turned the key to on (engine not running), and here's today's codes:

 

P0201 Injector circuit open cylinder 1

P0123 TPS/Pedal position sensor A circuit high input

P0301 Cylinder 1 misfire

 

I still like your approach of checking the health of the engine with the cylinder leak down test to tell its viability.  Armed with additional OBDII codes, does this now suggest the more immediate problem is in the electronics?  Should I be replacing the TPS sensor (throttle position sensor, I believe)?  NAPA had one for $60.  I have not yet looked at my Haynes manual to see what's involved.  I am interested in your feedback. 

 

I've enjoyed reading some of the other posts and the magazine.  I have a few more topics for future posts I can add later just to stir up some conversation.  For instance this Jeep of mine has been without 3rd gear (AX-15 5 speed manual) for a year or so (I just wind up 2nd gear and skip to 4th).  Also my airbag light is on and my cruise control no longer works (related?  clock spring?).  And it's got a bit of death wobble despite replacing a very worn out front track bar.  And lastly, I thought I read you were planning a write up about air conditioning - I've added refrigerant to mine in summer's past, but it doesn't last as long as it used to - looking forward to your future articles! 



#6 Moses Ludel

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Posted 16 July 2013 - 07:37 PM

Sounds like you've been busy and committed to a solution, JJ!  I like your pursuit of a leak down tester; this will demystify the engine's condition and seek out a possible compression loss that could cause a misfire.  Trust the tool will pay for itself on this engine work and other projects.  I've had my Snap-On MT324 for decades and am always pleased with its pinpoint diagnosis.

 

Your new codes do hint of a TPS switch problem.  I had a specific TPS switch issue/code around 110K miles on our XJ Cherokee.  I purchased an aftermarket Brand-X replacement, and it worked for a short time before causing a misfire string that resembled a short or burned wiring from the crankshaft position sensor.  Anyway, I sourced a second TPS from AutoZone on a Sunday, their own "brand", installed it, and no trace of a problem since. 

 

Some offshore stuff works, sometimes not.  As just one example, let's consider the oxygen sensor.  For Jeep and other Chrysler products, I specifically recommend genuine Mopar or at least ND brand as a direct crossover.  Denso was the OEM supplier to Chrysler, and oxygen sensors have very sensitive ohms feedback, heating functions and such.  See my article, this also applies to other electronic components in the fuel-and-spark management system: http://www.4wdmechanix.com/Use-OEM-Mopar-Oxygen-Sensors!.html.

 

I'd try a TPS, even though I'm set against "parts replacing" experiments.  The TPS is a wear item and prone to fail long before your 250K miles on the TJ Wrangler.  This would be the first order of business to see if the other two codes clear as well.  You'll find the TPS easy to replace; think of it as a spring loaded voltage rheostat or potentiometer.  The TPS fits one way with a slight tension as you install the switch and rotate it into position.

 

Your TPS does not require a voltage calibration, it's a straightforward replacement.  Exercise precaution with the aging plug connector.  Make sure the O-ring seats properly.  I use automotive dielectric grease on the plug connector contacts for a moisture barrier.  Considering how many issues can begin with a defective TPS, this is a good place to start.

 

It's actually good that you don't have several cylinders randomly showing misfire codes or acting up. That kind of issue is usually the PCM itself.  In any case, let's go a step at a time.  You might also run a continuity and voltage drop test on the injector plug at this nemesis #1 injector.  See this Geo Tracker post and my reply for more details on voltage drop tests and electrical circuit testing:  http://www.4wdmechanix.com/forums/topic/115-geo-tracker-sending-torque-converter-clutch-solenoid-code/.  Use a good quality digital volt-ohmmeter for these tests.

 

This approach will get results.  I would also disconnect the plugs at the PCM carefully, inspect the contacts and clean them only as needed, using electrical contact cleaner. Use automotive dielectric grease for a moisture and corrosion barrier when reconnecting these plugs.  Take your time with old connector clips and fragile lock release connections.  Protect these plastic parts. 

 

Let us know how this progresses.  I'm curious about the cylinder leak down results, too!

 

Moses



#7 jj_jeep

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Posted 18 July 2013 - 07:09 PM

I called the local Jeep dealer yesterday for a Mopar TPS.  It arrived today and my wife was gracious enough to stop by and pick it up for me.  It was $106 plus tax.  The auto parts store wanted $60 for a TPS - not sure what their brand was, but I was hoping with the new OBDII codes I wrote about last time, that a new TPS would alleviate the trouble, so I didn't want to mess around with a potentially flakey off brand sensor to save $40. 

 

I installed the sensor this evening.  One of the screws was a bugger to get out.  I did use a bit of liquid wrench and I tapped on the screw and after a time it finally worked loose.  I didn't want to strip out the small torx head.  It went just as you said, Moses, it kind of plugs in and rotates into place with just a little spring resistance.  I followed your recommendation and put a little dielectric grease on the rubber seal on the plug.  It seems like a pretty good seal design because the old plug was filthy on the outside, but clean on the inside. 

 

After installing the new TPS, I let the Jeep idle for a while in the driveway and then took the Jeep for a spin.  After more idling in the driveway, I am encouraged to report there has been no check engine light.  Normally idling at a stoplight would cause the engine to stumble and the check engine light would come on with the cylinder 1 misfire code. 

 

We'll see how tomorrow's drive to work goes.  But early indications are good that the TPS was causing me a lot of grief! 



#8 Moses Ludel

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Posted 18 July 2013 - 07:43 PM

JJ, this is good news...Trust tomorrow's drive will prove equally productive. 

 

The TPS should be considered a "perishable" wear item.  Think of the duty cycle and how many times that stem has wound up and down the tension and voltage curve in 250K miles.  In my own experience, the TPS and the wire from the crankshaft position sensor to the engine harness can deteriorate over time and create "gremlin" issues like you experienced. 

 

Another issue on engines with rear main seal seepage is engine oil on the toothed ring for the crank position sensor or on the sensor pickup itself.  Each can cause erratic error messages that often dance around the actual problem.

 

We're awaiting your update and optimistic.  It certainly was productive to change this TPS, and your Mopar parts choice assures accurate calibration of the new TPS.

 

Please share the follow-up!

 

Moses



#9 jj_jeep

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Posted 20 July 2013 - 01:52 PM

Day 2 with the new TPS.  After some idling in the driveway yesterday and the check engine light did come back on.  I don't own an OBD2 scan tool (yet), so I haven't been able to see what the current codes are indicating.  I did take the opportunity to clean up the battery connections since I disconnected the negative terminal to swap the TPS.  When I reconnected the battery I did notice that the negative terminal is not as tight as I'd like to see it.  It's the original factory terminal and cable, and after about 3 batteries and a few cleanings over the years, it's a bit worn out.  It's not going to come off, but I can wiggle it.  I don't suspect that it's causing any electrical problems, but I thought I'd mention it in case the forum thought otherwise.  A quick internet search seemed to indicate that purchasing replacement battery cables for a Jeep is not a straightforward thing to do.  Might make for an interesting topic/article, Moses.  I'm going to submit one under tools to see which OBD2 scan tool people like. 



#10 Moses Ludel

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Posted 20 July 2013 - 07:38 PM

JJ, sounds like that new Mopar TPS made a huge difference...Good news! 

 

The battery cable is very important, actually both negative and positive cables must be in good shape, as this is a D.C. system where both "hot" and "ground" circuits need the same amperage carrying capacity.

 

You need a consistent 12.4V or higher (12.6V or higher is a fully charged battery) for the PCM to be happy.  A bad cell in the battery or an open at a battery cable can stop the engine from running—even if the alternator still functions properly.  We experienced this with an intermittent 10.5-volt reading on the XJ Cherokee's battery.  The engine would barely keep running.  A replacement battery immediately eliminated the issue.

 

Looking forward to your posts, JJ!

 

Moses



#11 jj_jeep

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Posted 03 August 2013 - 05:30 PM

Just back from a good week at Scout camp with my son and his troop.  Based on Moses's feedback about battery voltage and battery cables, I spent a few minutes poking around my Jeep with a multi-meter just to try and rule some things in or out as the cause of the cylinder 1 misfire I'm having. 

 

These readings were all taken with the engine off. 

12.25 V probing from positive battery post to negative battery post

12.22 V probing from positive battery post to alternator housing

12.22 V probing from positive battery post to engine block negative battery cable terminal

2.3 ohms probing from injector 1 red wire connector to negative battery post (the cylinder that is misfiring)

2.3 ohms probing from injector 4 red wire connector to negative battery post (just a random other cylinder for resistance comparison)

 

With the engine running:

13.80 V probing from positive battery post to negative battery post

 

In short:

  • According to Moses' guidance, my battery is showing signs of wear (12.25 V I have is lower than desired 12.4 V), but I assume it's not enough to cause a cylinder 1 misfire. 
  • Battery voltage reads 13.8 V steadily with engine running - no issue there? 
  • Battery Cables don't look corroded, but they are covered with insulation and the OEM terminal, so can't really tell
  • Resistance of the one injector wire (ground I assume?) looked fine compared to cylinder that is not misfiring
  • Check engine light is on - haven't scanned the codes yet.  I'm assuming (and hoping) this will reveal a great deal more with a new TPS installed.  I don't have a scan tool (I borrow the one Napa loans out at their store) - started another post under tool and equipment sources to see which OBD2 scan tools people like and why as I'd like to pick one up. 
  • Cylinder leak down test - no progress yet - busy summer


#12 Moses Ludel

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Posted 03 August 2013 - 09:04 PM

JJ_Jeep...Glad you had some camp time with the troop and your son!  I read your findings, and the battery sounds shot.  After running, it should have from 12.6V (full state of charge) to 12.8V (common voltage for a freshly charged, newer battery).  12.2V is below par.  Not sure when you checked it, right after running, after setting a while, overnight?  This makes a difference.  If low after setting overnight and the battery case is very dirty, voltage can leak off the sides of the battery case or from post to post (a grounding discharge) and slowly discharge the battery.  Or you might have a slight drain from an accessory or whatever.

 

The best way I can illustrate this is to share a quick story about my wife Donna driving off with the XJ Cherokee after a sluggish engine crank over. (Most unusual, we wrote this off to the door being left open with the interior light on.)  Donna came home shortly thereafter, quite irritated, sharing that while she was at a stop sign, the engine died (again, most unusual!).  When she did get it going, the engine misfired and lacked power.  This is unheard of around our place because I do "preventive maintenance", a habit from my truck fleet mechanic days over forty years ago...

 

Anyway, I quickly checked the charging circuit, it read much like your findings.  I checked the battery immediately after shut-off, and the battery voltage was 12.7V.  Seemed okay, so I ran a simple load test.  AutoZone, NAPA and others will do this for free, in or out of the chassis.  In my case, I did a basic approach: turning on the headlamps with the engine off. 

 

Under this headlamp load, the voltage at the battery read 10-volts with the headlamps on just a few seconds.  Cranking would have dropped the voltage even lower. 

 

Try this with your volt-ohmmeter and headlamps on, picking up a voltage reading away from the battery to prevent sparks that might ignite a defective battery under load.  (Heavy battery lead contact at the starter motor is a good point, or even the alternator battery terminal.)  If your voltage drops to 10 or so, you've found what occurred in the Cherokee: a battery with a dead cell.

 

Now, if you do have a dead cell in the battery, it's possible that your engine will run erratically, just like our properly tuned Cherokee 4.0L did.  A dead cell is like an open, and regardless of the normal output from the alternator, the battery itself is not a reliable conductor of voltage to the PCM—or anywhere else.

 

I replaced the battery with new, and the problem immediately disappeared.  In your case, since I'm not comfortable with spending your money, try the load test with the headlamps on for a minute or so.  Or better yet, let AutoZone, NAPA, O'Reilly's or a similar "free test" outlet do a bona fide load test on your battery.

 

Replacing the battery is not a guarantee that your #1 misfire code will go away.  However, you can be assured that a defective battery will raise havoc with your engine's performance and reliability.  With the new TPS, I'm curious to know what code(s) the engine is now throwing. 

 

Read the stored codes before disconnecting the battery.  Deal with the battery and see if solving the battery issue cures any MIL or code problems...The ohms resistance from the injectors (red lead) to battery negative requires some thought.  The injector pulse width is a function of grounding at the PCM, not positive current switching.  We can discuss this further after you retrieve the codes.

 

We'll keep at this JJ!

 

Moses



#13 jj_jeep

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Posted 04 August 2013 - 12:05 PM

More good advice...  shopping for a scan tool to get the codes. 

Meanwhile, I took some more voltage readings... 

 

Lights and engine off

12.27 V alternator housing to alternator battery terminal

 

Headlights on, engine off

11.88 V alternator housing to alternator battery terminal



#14 Moses Ludel

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Posted 04 August 2013 - 01:30 PM

JJ, I would have the battery load tested, which simulates the cranking amperage draw.  To put this in perspective, a drained battery (still intact) will read 12V.  12.3V is 50% charged.  12.6V is 100% charged.  These are approximations.  Your battery is less than 50% state of charge at best, and below fully drained voltage with any kind of load.

 

This sounds like a "bad battery".  Load testing will confirm.  You're getting consistent 12.27V, so the battery seems to peak there.  The PCM likes 12.4V minimum, so this is a marginal situation.

 

How old is this battery?  Do you have aftermarket accessories or possible drains on the battery when static?  Assuming no draining down, and with daytime running to fully charge the battery, this battery is not in good condition. 

 

Did you catch my comments about a clean battery case?  We're all expecting better terminal connections soon.  Next stop: a load test, likely followed by replacing that battery.

 

Moses



#15 jj_jeep

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Posted 05 August 2013 - 07:29 PM

Should be able to check codes, then load test battery Friday with a stop at Napa.  Really curious about the latest codes.  Still thinking about the scan tool options for reading codes at home.  And the battery cables...  I might try a new terminal on the old ground cable to save cost until I know where I'm at with this misfire.  Battery is 6 years old - where did 6 years go?  No accessories, but it did sit for a couple weeks while we were gone to camp.  I re-read your comment about the clean battery case.  I've kept the battery blanket that came on the battery from the factory so it covers the case.  I'll check it out when I replace the battery. 



#16 Moses Ludel

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Posted 06 August 2013 - 11:00 AM

Six years on a Jeep battery is quite a while.  I use a Battery Tender in the winter on both of our magazine vehicles.  We also use a block heater, plugged in the night before starting the engine, in cold weather (below 45-degrees F and down to zero or lower in our neighborhood).  This is a necessity for the Cummins, as our traditional use of 15W-40 oil is daunting in cold weather.  I'm looking into alternatives here...

 

The Dodge Ram with Cummins engine should, by all accounts, eat up both batteries at around five years.  Due to the steady use of the Battery Tender, all winter and in other seasons when the vehicle sets for up to a week without a start-up, we have gotten nearly nine years out of the OEM batteries and they're still okay.  I've topped off with distilled water only twice in that timeframe.  (No complaints about OEM Mopar batteries here!)  I do expect replacement within a year; ten years for a diesel engine is amazing.

 

Our Cherokee, much like your Wrangler, does get battery use.  There's a winch that relies on a single 800 CCA battery, two Spal electric fans set to run after engine shutdown, and then there's the steady air conditioner use in the summer.  All tolled, five years of battery life is just fine here...

 

Let us know what you discover about your battery.  The terminal fix is a must.  Consider a Battery Tender, the best investment we have made in extending battery life!

 

Moses



#17 Moses Ludel

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Posted 06 August 2013 - 11:00 AM

Six years on a Jeep battery is quite a while.  I use a Battery Tender in the winter on both of our magazine vehicles.  We also use a block heater, plugged in the night before starting the engine, in cold weather (below 45-degrees F and down to zero or lower in our neighborhood).  This is a necessity for the Cummins, as our traditional use of 15W-40 oil is daunting in cold weather.  I'm looking into alternatives here...

 

The Dodge Ram with Cummins engine should, by all accounts, eat up both batteries at around five years.  Due to the steady use of the Battery Tender, all winter and in other seasons when the vehicle sets for up to a week without a start-up, we have gotten nearly nine years out of the OEM batteries and they're still okay.  I've topped off with distilled water only twice in that timeframe.  (No complaints about OEM Mopar batteries here!)  I do expect replacement within a year; ten years for a diesel engine is amazing.

 

Our Cherokee, much like your Wrangler, does get battery use.  There's a winch that relies on a single 800 CCA battery, two Spal electric fans set to run after engine shutdown, and then there's the steady air conditioner use in the summer.  All tolled, five years of battery life is just fine here...

 

Let us know what you discover about your battery.  The terminal fix is a must.  Consider a Battery Tender, the best investment we have made in extending battery life!

 

Moses



#18 jj_jeep

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Posted 10 August 2013 - 01:08 PM

Okay, I feel like we have a little more progress. OBD2 codes were reduced to a single code:  my friend the P0301 (cylinder 1 misfire).  The TPS code and injector code were not present. 

 

Battery checked out fine at NAPA - the store clerk came outside and connected their battery tester to my Jeep and he checked it with the engine off, on and on with headlights and HVAC fan on.  This surprised me after the lower voltage readings I got.  Must have been because the Jeep sat for a couple weeks before I measured the battery voltages?  I checked some voltages again today and got 12.66 V off, 13.74 V engine running, and 13.45 V running w/lights and fan.  Perhaps, Moses, as you mentioned a dirty case is bleeding off some voltage as it sits?  Not denying that I should get a new battery, but really desiring to understand what costs are in front of me to keep this Jeep running another year before I commit. 

 

There were no family plans for the weekend, so I've been tinkering and I think, Moses, I proved your point about the ground terminal replacement being a must.  Here's what I did:

 

1)  Disconnect neg batt cable from batt

2)  Connect a jumper cable to the neg batt cable so the jaw of the jumper had a nice, tight grip on the neg batt cable terminal

3)  Connect the other end of the jumper cable to the neg batt post (carefully keeping this birds nest away from the pos batt post and the engine belts and fan)

4)  Start the Jeep and let it idle with scan tool monitoring for codes (borrowed a scan tool from a friend at work)

 

Results - idled several minutes with no check engine light!  I am cautiously optimistic, because this is how things looked after idling with the new TPS several minutes, until the code returned the next day.  But I don't dare drive the thing around with dangling jumpers connected to the battery. 

 

Could we conclude from this, that a slightly loose negative battery terminal can cause a cylinder 1 misfire?  You recommended last post, that a neg terminal replacement is a must, and might resolve this misfire issue? 

 

Incidentally, a quick call to the Jeep dealer parts dept revealed battery cables are no longer "supported" for the 1998 Jeep Wrangler.  So apparently factory cables can't be sourced from the dealers. 



#19 Moses Ludel

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Posted 10 August 2013 - 03:39 PM

This is great, JJ_Jeep!  The battery is at least bringing normal readings, and the negative battery terminal has been a problem all along.  Whether this "cures" the #1 Misfire code or not, you needed to do this as a place to start, since you cannot get accurate readings or consistent performance any other way.

 

As for the #1 Misfire code, if this occurs again, there's an inexpensive way to test the #1 injector.  Try swapping the injectors.  Move #1 injector to any other cylinder (pick an easy injector to reach), and place that cylinder's injector in the #1 position.  With injectors swapped, clear the code(s), run the engine, and see if you throw a new code.  Drive the Jeep and see if you throw a code.

 

If you throw a #1 Misfire code, the original injector was not at fault.  If you throw a code for the cylinder where you placed the #1 injector, you know for sure that the problem is the original #1 injector itself (replace that injector!).  This is a fairly failsafe test and often a dealership troubleshooting technique.  Swapping injectors is not very difficult when compared to other troubleshooting steps.

 

Before swapping the injectors, try the terminal fix, and go from there.  You're making progress!

 

Moses



#20 jj_jeep

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Posted 10 August 2013 - 06:52 PM

After the jumper cable experiment showed some promise, I made a quick trip to the auto parts store and with Biggman's suggestion, picked up the marine terminal add-ons for the battery post and a couple copper crimps.  I wanted to try a quick and dirty fix to see if this battery terminal has been the issue all along. 

 

After a lot of idling in the driveway and a couple test drives, there was no check engine light! I was optimistic. 

 

I attached a picture of the cable.  Once I cut the 1998 factory battery terminal off and stripped some insulation, one cable had a little green here and there, but the other cable (the factory terminal has two cables - one for the firewall and one for the block) was heavily corroded.  Minnesota winters and road salt are probably the culprit here.  I stripped both cables back to clean copper, tried to "tin" them the best I could with the small solder iron I have, and crimp the copper terminals on (the other attached picture shows the two terminals attached to the marine battery terminal and the battery post. 

 

 Attached File  Battery cable corrosion.jpg   243.28KB   0 downloads Attached File  Battery cable terminal quick fix.jpg   181.7KB   0 downloads

 

Admittedly, it's a hack job.  The terminals were maybe a 1/16" big for the cable and, a neighbor crimped it for me with a tool slightly undersized for the job.  The guy at the auto parts did mention that they actually will make battery cables for me.  They have the "one-ought" cable and the $300 crimp tool and shrink tubing to do it.  But I wanted to complete a low cost fix first just to see if the misfire was an electrical problem or something more foreboding (read expensive) like engine wear requiring an overhaul. 

 

More to come...  but at present, that looks like new battery cables.  Expect an update. 



#21 jj_jeep

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Posted 11 August 2013 - 03:03 PM

The menacing P0301 cylinder 1 misfire came back.  But not to be deterred, I tinkered with the injectors a bit and found some odd behavior.  My neighbor saw the hood up and came over and asked what it does if you unplug injector number 1.  We did and nothing noticeable happened.  Hmmm, that doesn't seem right.  So we confirmed by unplugging injector #4 instead, and then the engine stumbled MORE.  I checked the codes and you get a P0201 or P0204 depending on which injector you unplug. 

 

Moses, you suggested swapping injectors.  I would like to do this and just double confirm that replacing the injector is the fix (versus say replacing the electrical connection to the injector if the problem stays with cylinder 1 for instance).  Is it best to have the proper O rings on hand for putting these injectors back in place?  Or do they come out and go back in pretty easily? 

 

I've read the procedure for doing it - in rough outline, you relieve pressure in the fuel rail, then unbolt the fuel rail and pull the rail and injectors from the manifold.  At that point I can swap #1 with one of the others and repeat the procedure in reverse...  Any tips here for avoiding creation of new problems? 

 

In the event that the problem follows the injector indicating the injector is bad, I see various options for dealing with it.  Is there "better" logic to one of these options over another? 

1)  Replace the bad injector and move on with life. 

2)  Replace all 6 injectors (are injectors an item where it's recommended to replace all together, rather than just one?)

3)  Replace all 6 injectors with the higher pressure injectors for the potential stroker build some time in the future.  Do the injectors recommended for strokers perform fine with a stock (albeit old) 4.0 L? 



#22 Moses Ludel

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Posted 11 August 2013 - 06:55 PM

It would pay to have some correct O-rings on hand, as they do not cost that much, and you anticipate stroker injectors in the future, anyway.  Since you do anticipate the stroker build at some point, I would just replace the one injector, if defective, with a stock 4.0L rebuilt type.  They are readily available from GB and others, through your local auto supply and outlets like AutoZone.

 

Replacing with "stroker" injectors at this point would be ill advised.  You are not sure of the engine's condition, but the engine has high mileage.  Compression and cylinder seal are still uncertain, so higher flow injectors would certainly not help.  In fact, the fuel enrichment could shorten the remaining service life of the stock engine.

 

Do the injector swapping that I suggested and see the results.  This is the quickest approach and could lead to, at most, a new injector that you know is needed.  As for the injector wiring harness, connectors and all of that, you'll narrow the trouble with the injector swap.

 

This has become a popular topic and replies.  I'm glad to offer further help.  Let us know the outcome... 

 

Moses



#23 jj_jeep

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Posted 15 August 2013 - 07:33 PM

The fuel rail is kind of a pain in the neck to wrestle off and on.  After considering the prospect of doing it twice (once to swap injector #1 to another cylinder, and then a second time to swap in a new injector), I was thinking I would prefer doing it once.  I stopped by the auto parts store and they had the injector in stock, so I made the $70 bet that the injector was the problem and bought it.  I finished swapping the new injector onto cyl #1 tonight. 

 

After the TPS and the new ground battery cable terminal looked good for a day, and then weren't the final fix, I don't want to jinx the injector!  So we'll see how it runs through the weekend, but suffice it to say the light is not currently on. 

 

For the uninitiated, swapping an injector was a doable task for a novice. 

I followed the Haynes manual which advised disconnecting the neg batt terminal, opening the fuel cap, and relieving the fuel pressure from the fuel rail at the Schrader valve into a rag.  There's a good amount of fuel that comes out, so I left this rag outside to air out.  Note that later, as you remove injectors to replace the O-rings, there is more fuel in the fuel rail that can spill out.  Keep lots of old socks handy. 

The air intake comes off fairly easily - it helped me to remove the air filter cover end of the intake and then rotate and pull the intake at the throttle body. 

Next the throttle cable bracket comes off.  I tucked the cables under the rod that goes from the grill to the firewall and that pretty much kept them out of the way. 

Four bolts hold the fuel rail on the intake manifold.  The one by the firewall also held a sensor in place, so there's a nut to remove first. 

The fuel rail takes some patience and elbow grease to pull it free from the intake.  I must admit my wife had the brilliant suggestion of shooting a little WD-40 on the injectors at the air intake to help wiggle them free. 

Once the rail was loose, I left the fuel line attached since it's flexible hose and I just flipped the fuel rail and tied it in place so I could remove the injectors.  I cleaned up the injectors with WD-40 and a rag and put new O-rings on them and swapped the offending injector from cylinder 1.  I lubed the O-rings with WD-40 to put the injectors back in the fuel rail. 

Everything goes back together in reverse order. 

When done, I did take the precaution to turn the key to "on" to run the fuel pump and pump up the fuel rail and checked under the hood for fuel leaks.  I thought I'd rather discover a leak before I started the engine.  There were no leaks, but thought I'd pass this along. 

Drove it around a bit.  Seems less prone to burbling and backfiring when I get out of the throttle. 

More to come... 



#24 Moses Ludel

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Posted 16 August 2013 - 09:51 AM

I almost suggested that you change the #1 injector rather than do the job twice.  However, I was reluctant to spend your money.  At the engine's mileage, the original set of injectors has been thoroughly worked.  Your description of the task involved builds a good case for simply replacing the #1 injector.

 

This is a valuable "how-to" for those needing to change an injector, JJ_Jeep.  Thanks much for taking time to share in detail.  Looking forward to this weekend's test driving and results, an update on whether this ends the misfire code.  If so, credit to Chrysler/Jeep and OBDII for an accurate DTC (Diagnostic Trouble Code) reading!

 

Was there anything "suspicious" about the look of the old #1 injector when compared to the others?  Did you see anything unusual at the nozzle end?  If so, could you please attach a photo of that injector's nozzle?

 

There are many followers of your topic, and it's been a good opportunity to air the issues around injector codes and defects.  Thanks, JJ_Jeep!

 

Moses



#25 jj_jeep

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Posted 18 August 2013 - 06:50 PM

Well, so far, so good.  After replacing injector #1, I have not seen a check engine light. 

 

The injector nozzle end didn't look suspicious to me.  I do wonder about the other end - is there a screen in there that can clog?  I'll try to get a couple pictures of the bum injector at work.  And we'll see if the check engine light stays away! 

 

Still thinking about that cylinder leak down test.  I'd like to know the health of this engine before I move on down the list of other work this Jeep needs.  The link you provided has the lowest price I've found.  And OTC seems to be the best "entry level" model out there.  Summit Racing has a nice package that comes with a stethoscope and a compression tester, but was quite a bit more money.  Other brands seem to be limited in the pressure they can use or read. 



#26 Moses Ludel

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Posted 19 August 2013 - 07:40 AM

JJ_Jeep, this is good news!  If the MIL stays out, you have a single-part cure here!   OBD-II, in this case, has narrowed your diagnostics and proven cost-effective.  That was the original aim of the Federal mandate for OBD-II, which opened up dealership, proprietary engine diagnostics to independent shops and, eventually, hands-on consumers. 

 

The simplicity and standardization of tester plugs, with common DTCs (diagnostic trouble codes), makes even a $30 aftermarket code reader or $100 real-time scan tool a place to start.  Today, the "real time" functionality of inexpensive scan tools makes powertrain device troubleshooting much easier and places diagnostics in the hands of consumers and smaller shops—often short of the need for a $6,000 tool. 

 

Sure, there are limits to the code readers and basic scan tools, but in your case, the trouble was specific and identifiable with just a reader.  To the point, a "#1 Cylinder Misfire" was the code read, and not surprisingly, you wound up with a defective injector.  The reader narrowed the field to either a wiring issue or as you apparently have found, the likely trouble:  a misfiring injector.

 

So, if this is the cure, OBD-II did its job.  Sometimes, the DTC (diagnostic trouble code) is a generalized reference to the trouble, but in the case of a #1 Cylinder Misfire, the read is more explicit.  Still, it paid to do some checks and tests before replacing any parts, and that's true mechanics, and not just being a "parts replacer".  Thanks for going along with the process, JJ_Jeep!

 

You asked if there is a filter or screen in the injector, and yes, there is one.  Here is a generic injector illustration from Wiki that helps explain the injector firing process.  You'll find the animated illustration helpful:

 

http://upload.wikimedia.org/wikipedia/commons/2/29/Injector3.gif

 

As for assessing the overall engine condition, the OTC leakdown tester would be a good investment.  Your volume of usage for the tool may not justify buying one, though.  For that reason, I'm posting a topic on how to make a very inexpensive home use tool, and I'll explain its usage.  Again, we're after affordable solutions, and this is one I'll post at the "How-to Tips" forum category.  I'll also post comments on the use of a vacuum gauge as a simple, overall engine tester.

 

Keep us posted on your MIL/check light and the engine's performance.  On that note, is the 4.0L engine running "better"?  If the engine runs noticeably better, please share with us the actual difference and how a #1 Cylinder Misfire impacted performance.  What was the "before and after" effect of replacing that #1 injector?

 

As a footnote, it's great to fix an engine and extend its service life a bit.  Every day you drive the TJ prior to rebuilding the high mileage engine is money in your pocket.  As long as the vehicle is safe, reliable, reasonably fuel-efficient and there's no risk of damaging the engine in a way that would prevent rebuilding it (like, say, running the engine with bad crankshaft bearings and chucking a connecting rod through the side of the block!),  you're ahead of the game—and without a $500 a month payment for a new vehicle.  $70 for a single injector?  If this is the cure, it sounds like a bargain!

 

Moses



#27 jj_jeep

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Posted 20 August 2013 - 07:16 PM

I really like the guidance OBD2 offers.  And I think the cheapest scan tool out there is probably the best one for most novices like me that are going to tackle problems that haven't disabled the Jeep but have turned on the MIL.  Because I'm going to take the code directly to the internet and look it up.  The scan tool doesn't have to offer advice. 

 

I've been carpooling to work ever since gas prices jumped ~5 years ago, so the TJ doesn't get 20k miles per year on it like it used to.  I drove it a bit over the weekend and took advantage of the beautiful weather this evening and drove to the next town and back with the top down and the radio up.  The engine is running much smoother.  Idling at red lights you really notice how much smoother the engine is running - the rig doesn't shake and vibrate - and so far, no check engine light.  I think the new injector has about 35 miles on it, so things are looking up.  The engine also doesn't lug down and growl as loudly anymore either.  In residential areas I'm in 4th gear, because the 3rd gear synchro is shot (I think - a future post I'd like to make - but I'd like to check leak down to estimate what kind of life this engine has left before I think about the transmission).

 

There is a small hill nearby that made 4th gear in the Jeep sound like a semi truck creeping up Pike's Peak in the wrong gear.  With the new injector, it's not nearly as loud (a little hard to tell, because I think I have a cracked header - but there's a difference) and I don't have to jump down to 2nd gear to get up the hill.  And after driving it, there's no gas smell under the hood (gas smell showing up in the exhaust through the cracked header?). 

 

Here's some hi magnification pictures of both ends of the bum injector #1.  I've never looked at an injector before, but by my estimation nothing is wrong with the orifice of the injector.  The O-rings also appeared OK.  I'm left to wonder if the filter screen was clogged or if the solenoid in the injector was malfunctioning. 

 

Attached File  old and new injectors.jpg   147.12KB   0 downloads

Old and new. 

 

Attached File  Injector Fuel Rail End.jpg   67.82KB   0 downloads

Fuel rail end.

 

Attached File  Injector Fuel Rail End Filter Screen.jpg   44.74KB   0 downloads

Screen inside fuel rail end.

 

Attached File  Injector Manifold End.jpg   65.6KB   0 downloads

Manifold end. 

 

Attached File  Injector Manifold End 2.jpg   64.4KB   0 downloads

Another one of the manifold end. 



#28 Moses Ludel

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Posted 21 August 2013 - 10:46 AM

Fantastic close-up photos, JJ_Jeep, thanks for sharing!  Looks like enough carbon and soot for an injector problem, and you are likely spot-on about the filter/screen or solenoid issue.  Moot point, as there's plenty here to cause a misfire.  Glad you could narrow this down and merely buy the injector. 

 

As for what I see here, is the 4.0L using much engine oil?  Looks like a possible ring blow-by or valve guide and seal issue, possibly oil or soot spitting back at the injector.  Did the other injectors have this oily, soot look around the injector end?  Does the #1 spark plug show carbon buildup or a sign of burnt oil at the tip or electrode?

 

Oil consumption would certainly be justified at 250,000 miles, along with a drop in compression.  Try my simple vacuum test at an idle, I'd like to know the idle manifold vacuum and how steady the needle looks on the gauge.  You may have carbon buildup around the valve seats and combustion chambers;  this would not be surprising for the mileage.  We'll keep in mind that we're simply trying to have this engine run well until you decide on either a stock or stroker motor rebuild.  Normal wear for the mileage is expected.

 

For those interested, there are also rebuilt injectors available, one example is from GB Remanufacturing, a supplier to AutoZone, HESCO and others:  For your engine application, JJ_Jeep, the part number is a GB 812-11128

 

As for the lowest possible price on this injector (per injector, not the full set), I quickly found this at Amazon:  http://www.amazon.com/dp/B002NF10SQ/ref=asc_df_B002NF10SQ2667297?smid=ATVPDKIKX0DER&tag=pg-93-01-20&linkCode=asn&creative=395097&creativeASIN=B002NF10SQ.  $35.75 plus free shipping.  This 812-11128 part number fits JJ_Jeep's 1998 TJ Wrangler 4.0L inline six-cylinder engine and other '97-up Jeep applications.  Confirm the fit for your engine.  New injectors are available from Mopar and a variety of other sources.

 

If you need more information on the 3rd gear synchro, see the AX15 discussion here at the forums and my step-by-step rebuild of an AX15 at the magazine.  It's a two part how-to with 209 studio level photos...Kind of like your great pics of the injectors, JJ_Jeep! 

 

Moses



#29 jj_jeep

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Posted 21 August 2013 - 07:20 PM

When I pulled the fuel rail, the manifold end of every injector was sooty and dirty like that.  In fact, the manifold holes had a ring of soot around the outside too.  I tried to wipe the manifold holes off a little with a rag, but I also didn't want to mess with it a lot and risk pushing that stuff into the manifold.  I cleaned every injector with a rag and WD40 when I changed the injector O-rings. 

 

When I pulled the dispstick at the last oil change, it was still in the hatched "safe" zone.  I have never had to add a quart to this engine.  I attached a picture I took of the #1 and #6 spark plugs a while back when I was verifying that the misfire wasn't plugs or plug wires. 

 

Attached File  Spark Plugs 1 and 6.jpg   153.65KB   0 downloads

 

I liked your write up on the vacuum test, so I picked up a gauge tonight and made a quick video of the vacuum gauge on my TJ. 

 

Attached File  Jeep Vacuum.wmv   21.8MB   7 downloads

 

I am encouraged that the vacuum seems to be decent considering the miles on the engine, but the needle does wiggle.  And the vacuum drops considerably when I throttle up to 2k RPM and then let the throttle slam shut.  That said, at 2k RPM, it does pull 21 in hg.  Manifold vacuum also bounces up and down when I pump the brakes and release the brakes.  Not sure if this says more about the brake booster or the engine? 

 

Third gear - I've skimmed through your writeup on the AX15 rebuild.  I've never changed a clutch or even dropped a tranny, so I must admit it looks intimidating.  Would you say it requires more skill, or just great care in keeping track of all the parts and putting them together in the right order.  Interestingly, I did call a tranny shop a while back about this and I was surprised they didn't want to touch it.  They thought I'd be better off with a tranny swap.  I thought if people rebuild these at home, a tranny shop would certainly do it for three digits... Not sure if that means it's difficult, or just really time consuming to rebuild?  You might be able to talk me off the ledge.  I've certainly dug into this misfire with your guidance!  Really interesting, and pretty fun to get results. 



#30 Moses Ludel

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Posted 21 August 2013 - 08:58 PM

Watched the video, JJ_Jeep, and this is great.  (I'm linking from the vacuum gauge post to your .wmv here, it's a very useful and live illustration!)  The plugs look quite good, and your vacuum readings for closed throttle and 2000 rpm are more than acceptable!

 

The needle fluctuation is well within the norms for a vacuum reading.  Unseated or burned valves would have the needle swinging quite widely as it flutters.  Your engine is in good condition for the mileage and begs the question:  What kind of oil have you been running and which filters? 

 

This engine likely has timing chain wear.  I say this because the manifold vacuum actually picks up with engine speed, which can indicate spark or valve timing retard at an idle.  I have a very quick test for timing chain wear if you're interested.  This would separate ignition timing from valve timing issues.  In any case, the indicated wear is likely not enough to bother changing the timing chain and sprockets—unless there is noise.  Besides, you're not getting a camshaft DTC or MIL.

 

If the engine is running quietly (no timing chain noise) with good oil pressure and no significant oil consumption, assume you have miles left in this 4.0L six.  Of course, a leakdown test would offer more insight, but you have valuable information already from the vacuum test, and it does look good!

 

As for the brake booster/vacuum response, this is normal.  The booster reservoir drops vacuum with each brake pedal application, there's a void, and the engine vacuum must refill the booster, all very quickly, of course, but this is a vacuum drop.  You don't feel this when driving, as the booster refills quickly.  Normally, your foot is off the throttle as you apply the brakes, so manifold vacuum remains high.

 

Regarding the AX15 transmission, you have good instincts.  Rebuilding the AX15 is not for the faint of heart.  I like to put this level of how-to out for owners so you can make an informed decision about whether this is a job for your home shop.  I'm very clear about the tools involved, including pullers and a press with fixtures, feeler gauges and hand tools.  I do include tools you can improvise to avoid a large tool expenditure for a one-time job.

 

I like to call a transmission like the AX15 a "close-tolerance", close fit-up unit.  Since I have been rebuilding both manual and automatic transmissions professionally for 44 years, I'm in a position to be straightforward about the skill level involved:  The AX15 is a transmission benefitting from previous experience at transmission rebuilding.  Having said that, I also know that many with moderate experience have followed my detailed steps and pulled off a thorough and proper rebuild.

 

If you find the rebuild idea daunting, there is a recommended alternative:  Advance Adapters sells brand new Aisin AX15 transmissions that just happen to be direct fit for the Jeep TJ Wrangler applications like yours.  I heartily recommend considering a new unit if you plan to keep the Jeep Wrangler for a long time (like the TJ's first go-around), especially if you're considering a power upgrade to the 4.6L stroker motor.

 

Moses



#31 biggman100

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Posted 21 August 2013 - 09:29 PM

JJ, although it sounds like you have the misfire problem fixed, i wanted to add one small bit of advice for anyone else who reads this. Dont overlook the O-rings on the injectors themselves. I chased a misfire on a Cadillac escalade for weeks, and after i finally got frustrated with it, i took it to Cadillac, and they traced it to a small tear in an injector O-ring. That experience taught me a valuable lesson. Never rule out even the smallest thing.



#32 jj_jeep

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Posted 22 August 2013 - 07:09 PM

O-rings!  Biggman, I think the O-ring is the bane of modern man.  They often serve such a key function, yet they usually are wedged into a small space to create a seal and you can't verify if you damaged it during installation or not.  The space shuttle Challenger disaster was said to be due to a flawed selection of O-rings that failed in the unusual air temperature on launch day. 

 

For oil and filters, I never did anything fancy.  When the Jeep was new, I always used Motorcraft oil.  When that became harder to come by, I ended up switching to Valvoline.  I have always followed the owners manual running 5W-30 in the winter and 10W-30 in the summer.  During the misfire issue, I've been running Mobil high mileage 10w-40.  I hesitate to say the filters I use as some might consider them a 4 letter F word.  I can only think of a couple times where I stretched the oil change interval to 6k or 7k miles, otherwise it was always about 5k miles.  My commute for 15 years has been straight highway with cruise set to 60 mph - really easy miles on an engine.  It's probably why I'm still on the original clutch (although it seems to be on it's last legs) and the original brake rotors. 

 

When I first started tinkering with the misfire, I was having a noisy tick coming from the engine too.  I suspected a stuck lifter and I thought, I have nothing to lose, so I tried a half can of Sea Foam in the crankcase for a couple thousand miles and then drained and filled with 10W-40.  That seemed to loosen the stuck lifter - or at least alleviate the ticking if it was something else.  Of course, it took a new injector to solve the misfire. 

 

I've looked at the Advance Adapter ax15 and that looks pretty good.  I wonder what the degree of difficulty is on a tranny swap and a new clutch. 

 

Moses, I am interested in the quick timing chain wear test.  In the course of the misfire diagnosis, I looked through my records and I can't say for sure that the timing chain/sprocket have ever been changed. 



#33 Moses Ludel

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Posted 22 August 2013 - 09:05 PM

JJ_Jeep, your 250K miles with this little in the way of repairs and service parts is an indication of quality, highway mileage and conscientious routine maintenance. Good work there!

 

The AX15 from Advance Adapters should be a bolt-in without modifications.  There will be a transfer of some peripheral parts, nothing difficult there.  A quality clutch replacement with new disc, throwout bearing and a new clutch cover, plus a new pilot bearing and resurfacing or replacement of the flywheel, would do it!

 

I'll post the timing chain test at the Let's Talk 'How-to Tips' forum...

 

Moses



#34 biggman100

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Posted 22 August 2013 - 09:31 PM

JJ, to add to your question about rebuilding your transmission, and also a minor note to Moses, unles you have considerable experience with the inner workings of any manual transmission, rebuilding the AX15 isnt something i would try myself unless Moses was standing over my shoulder watching. As some already know, i have a 1994 Dakota with an AX15, that had some issues, which is what first brought me to this forum.

 

In finding the part i needed to fix mine, which i finally found a few days ago in the form of a used AX15 that had internal gear issues, i found that that transmission can be a bear to work on. All i was replacing was the extension housing on mine, which is the rear piece the transfer case and shift lever attach to, and just getting the one off the transmission i bought, even going by the pics and info Moses posted in his AX15 rebuild, it still wasn't easy to get apart.

 

After finally getting that part off, i decided, since i have never taken one apart, and the one i had was mainly a parts transmission anyway, to go ahead and dissasemble the rest of it, just to see how everything worked inside, and even with all the info Moses posted, and all his help, i found that just taking that transmission apart isn't an easy task. Im not saying that you couldnt do it, but if you do, i would have a computer next to you, with Moses' write up already open on the screen, and be prepared for some unexpectedly heavy parts, and stubborn, hard to remove parts as well.



#35 Moses Ludel

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Posted 22 August 2013 - 09:53 PM

Biggman100, I appreciate your compliments, the article and its illustrations are a "textbook" approach to rebuilding the AX15.  I was diplomatic when I shared that this transmission rebuild is not for the "faint of heart".

 

I've had very supportive comments from many who have rebuilt an AX15 from the steps I share and that level of detail, which, quite frankly, is beyond a factory workshop manual, since a workshop manual lacks the number of photo-illustrations and is shorthand for professionals who already have a sense for transmission rebuilding.  On the other hand, I have not polled the folks who rebuilt their AX15 to determine what previous experience they brought to the task...

 

I instructed automotive mechanics a total of seven years at the adult education level, writing curriculum for five of those years.  Bringing that experience to projects, I want the reader to "think like a mechanic".  (Excuse me, we're "technicians" today.)  I'm an optimist and instructor who believes that information translates as ability.  I've been known to overestimate the number of folks who either want to think like a mechanic or have life experience that supports that "thinking".  

 

I like JJ's hint, and we could employ a skill/difficulty rating for projects, setting up criteria for what each rating really means.  This is popular elsewhere and would be a sensible way to forewarn folks of a project's challenges.

 

Moses



#36 biggman100

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Posted 22 August 2013 - 10:08 PM

Moses, i second JJ's hint about adding a difficulty system. When i took apart the AX15 i picked up, i made sure to follow your write up very closely, but, even with the write up, some parts were a bit difficult to disassemble. And, i also had downloaded a copy of the AX15 part of the shop manual, and i agree, it didnt cover the rebuild near as well as you did.



#37 Moses Ludel

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Posted 23 August 2013 - 12:30 PM

I've opened a new topic at the "Let's Talk" category about this idea of ranking projects...Thanks, JJ_Jeep and biggman100 for the input!

 

Moses



#38 jj_jeep

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Posted 26 August 2013 - 07:41 PM

Still no check engine light! 

I'm calling the misfire "fixed" by replacing the fuel injector. 

Thanks for all the advice Big and Moses... 



#39 Moses Ludel

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Posted 27 August 2013 - 12:50 PM

Yea, one down, just the Air Bag light to go!  Glad this worked out, JJ_Jeep...

 

Moses



#40 bamafan1

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Posted 28 December 2013 - 06:47 PM

Folks I need some help with the same P0301 code. I've owned this TJ for 26 months. No other codes have shown up and this one has been intermittent. By intermittent I mean the check engine light comes on and stays on for a few weeks then has gone off without use of a scanner. It currently has 131,000 miles since Agust 2013, I've done the following:

 

Changed plugs, wires, distributor, rotor button. Cleared code, it came back. Seafoam-ed the engine, cleared the code, and it came back. Changed #1 plug from an Autolite AP985 to a Champion 412. Cleared code, and it came back. Paid local mechanic to do vacuum check and swap #1 & #3 injector. As you guessed, cleared code and it came back. Any ideas, advice, special prayers?

 

I would appreciate any help anyone can offer. Just as an FYI, I've had access to a Matco MD80 scanner ($550 retail) and a $4,000 Matco (don't remember it's model number). I include that just to let everyone know that I've not been using $10 scanners to clear the code (maybe that's the problem). Again, I appreciate any ideas/advice.



#41 Moses Ludel

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Posted 29 December 2013 - 07:13 AM

Bamafan1, welcome to the forums!  We've had a lot of discussion about the #1 misfire code (P0301). Your swapping injectors reminds me of the only factory warranty repair ever made to our '05 Dodge Ram 3500 with the Cummins engine. This story may be helpful and clarifies the limitations of both OBD-II and PCMs...

 

We purchased the truck new, and it had only 800 miles on it when we drove from northern Nevada to Pomona, CA for an Off-Road Expo event. En route, we broke up the trip, staying overnight at a motel in Ridgecrest. The next morning, the truck started up with several cylinders misfiring and would not correct itself until the engine warmed. I thought this was a warm-up cycle problem, but by the time we got home, misfiring became random. I approached Carson City Dodge, where Eric Benson, one of the best Cummins/Dodge techs in the country, took on the warranty fix: The code was a #1 cylinder misfire.

 

Eric installed a new injector and even swapped injectors (cylinder to cylinder like you did) to no avail. The #1 code would occasionally become other cylinders. He checked for poor injector grounds (uniquely, with a lamp load test, a very smart and quick method) and found none. In consulting Chrysler, Eric asked if the PCM could be at fault. He discovered that there were 25 similar trucks from our new truck's cohort group stalled at dealerships with exactly the same issue. Chrysler insisted that the PCM would self-interrogate and send a DTC if it had a defect. Eric was suspicious and asked Chrysler for permission to change the PCM. They balked for over a week and finally allowed Eric to change the PCM.

 

This was the first approval by Chrysler for a replacement PCM, and the "Cummins Recon" (reconditioned by Cummins) replacement PCM immediately cured the problem. The truck has over 125K miles on it now and recently got the Hypertech re-flash tuning program—without missing a beat!  Eric was not only right, but Chrysler just recently sent all owners of our truck model/year group a nice notice extending the warranty on the original PCM indefinitely. Obviously, the PCMs were defective, and none of these flawed units sent a DTC code to let us know!

 

My point is simple: Scan tools are wonderful within certain parameters. When all else fails or there is a random problem, it is probably wise to at least unplug (carefully, do not break latches!), clean contacts and re-plug the PCM connectors. As for a problem like yours, where swapping the injectors did not cure the problem, you might want to do a ground check on the #1 cylinder/injector wiring. Eric's quick check with a lamp load test is very smart, as the Chrysler systems are live wiring to the injector: The PCM completes the ground. You should have no problem performing a lamp load test.

 

You do not describe an actual cylinder misfire at #1. (This could easily be viewed with an engine analyzer scope test of the ignition performance. Lean or rich fuel misfire also affects the ignition voltage requirements and changes the ignition firing spike heights on a traditional oscilloscope ignition spark analyzer test.)  Sounds like the communication between #1 and the PCM could be touchy. Read the comments above from other owners, and let's get to the bottom of your #1 cylinder misfire DTC!

 

Moses



#42 bamafan1

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Posted 29 December 2013 - 09:14 AM

A noid test was done when injectors were swapped (forgot to include that) and the noid test checked ok. What's the best way to clean the PCM - can of air like for laptop? CRC contact cleaner?



#43 Moses Ludel

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Posted 29 December 2013 - 01:21 PM

The PCM plug contacts and electrical connectors can be cleaned with electrical contact cleaner. I personally use the official Mopar Electrical Contact Cleaner:

 

Attached File  Mopar Contact Cleaner.jpg   19.07KB   0 downloads

Mopar Electrical Contact Cleaner Part Number 5018045AA.

 

I'm curious how corroded or "black" the contacts look before you clean them. Some recommend soda blasting; however, use real caution and be sure to ground the PCM from static electricity during the soda blast. Like with any computer, static electricity could blow out the PCM. 

 

Attached File  Corroded Pins on a PCM or ECU.jpg   64.34KB   0 downloads

This is a glaring example of the kind of "black" corrosion described in Mopar service literature. (Example borrowed from another internet forum, actually a G.M. ECU.—Thanks!)

 

Another area where the contact cleaner works is the crankshaft position sensor (pre-coil-on-plug 2.5L and 4.0L engines). The sensor atop the bellhousing lends itself to debris and even rear main seal oil contamination on higher mileage engines that weep oil.  Though a dirty CPS should throw a CPS DTC code, it may not. Misfire, erratic running and other symptoms are common with a dirty CPS pickup.

 

   Tip: See the magazine's article on the gauges/bus issue for Cherokee models. Also useful is a Vlog Q&A that I did on electrical connections:  http://www.4wdmechanix.com/Q&A-Vlog-Testing-Ground-Circuits-and-Wiring-Integrity.html. I'm not implying that you need new connectors on your TJ's PCM; simply emphasizing corrosion issues at the PCM/ECU/ECM connectors.  You'll need to determine the extent of corrosion or any damage.

 

Please let us know how this turns out.  A lot of your symptoms point to the possibility of poor connectivity or "messaging" between the PCM and injectors.  The #1 Cylinder Misfire DTC is a common fault code, apparently an occasional catchall for unrelated causes and issues. 

 

Moses



#44 bamafan1

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Posted 29 December 2013 - 03:12 PM

Moses, I really appreciate all the advice/ideas. I'll follow this avenue and see what happens.



#45 bamafan1

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Posted 30 December 2013 - 09:16 PM

Moses, bought the cleaner today. Removed CPS, and as I started I noticed the bolts were loose enough to turn by hand. Not sure why they were loose as it has not been touched (to my knowledge) since I took owenership 26 months ago. Cleaned everything very well and re-installed. Then moved to PCM. Removed and inspected but it barely had any dust on plugs under cover. Pins were clean and still had the shiny brass look. Re-installed PCM. Cranked it and no check engine light. I did not clear code before or after this step. Drove it about 10 miles and so far so good. Obviously I'm not 100% sure that it's corrected but going to keep my fingers crossed. Will see how it goes and advise again soon. Again, thank you for your time and help.



#46 Moses Ludel

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Posted 31 December 2013 - 07:25 AM

Sounds like the CPS pickup did need attention, glad I mentioned that one.  Loose and not accurately picking up a signal, the CPS could cause a #1 misfire code.  The CPS references TDC on #1 cylinder.

 

Sometimes just unplugging and re-plugging an electrical connector can resolve a subtle resistance issue.  It's actually amazing that the PCMs function as reliably as they do.  A PC computer would rattle to death on the first 4WD trail, likely split the motherboard in half.  PCM connectors must carry finite, precise voltage signals with accurate data messages.  To their credit, the PCM and connectors do hold up for a very long time.  To a degree, the later CAN-bus systems have reduced room for errors, as the number of wiring circuits get reduced.

 

Let's watch while you get some miles on the clock...If this clears up the code issue, the cause could have been the erratic TDC/#1 cylinder signal from a loose CPS or resistance at a plug connector (which went away with the unplug/re-plug).  Please keep us posted, bamafan1! 

 

Enjoy the forums, all of us look forward to your participation.  Have a Happy New Year!

 

Moses



#47 bamafan1

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Posted 31 December 2013 - 01:57 PM

Well, drove 2 miles this morning and it's back. Checked code and it's still P0301. I'm sure there's a logical explanation, however, I'm not smart enough to figure it out.

#48 Moses Ludel

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Posted 01 January 2014 - 12:05 PM

Well, Happy New Year, bamafan1, and let's keep working on this!  Is there actually a drivability issue or a "real" symptom associated with the #1 cylinder misfire code? Or are we simply getting a MIL/DTC code for P0301?

 

Moses



#49 bamafan1

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Posted 01 January 2014 - 12:15 PM

Happy New Year!!! No obvious driveability or performance issues, just getting the code. While I know it's not about to "die", it bugs me because I know there's a reason, whatever it may be, that's making it come on.



#50 Moses Ludel

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Posted 01 January 2014 - 01:25 PM

Well, if it's any consolation, here's a mirror of your problem at the Jeep Forum, dating to 2008: http://www.jeepforum...stumped-564707/.

 

I would agree that any of the factors shared in that exchange could play a role in a false or touchy P0301 DTC. However, when looking down the laundry list of suggested fixes or trouble spots, the item that jumps out for me is the TPS.  This switch is a wear item: imagine a rheostat or potentiometer changing the voltage every opening and closing of the throttle!

 

On our XJ Cherokee 4.0L, I changed this switch as a matter of course. They are not expensive and certainly more subject to heat, wear and fatigue than a MAP or other sensors.  The temp, O2 sensor or cat is usually a code-specific weak point, anyway...DTC for these other sensors, or even a highly out-of-whack TPS, are usually accurate in OBD-II.

 

Consider testing the TPS voltage readings and the smoothness of response on the voltage sweep from idle position to WOT.  If you do decide to replace the TPS, I did okay with an Auto Zone sourced switch and previously had issues with a Standard brand.  Mopar, of course, would be the best device for calibration, though more expensive.  On the 4.0L MPI engine, this switch mounts in a fixed position and is not voltage adjustable like many TPS switches.

 

If you need an orientation to the test procedure for a Jeep 4.0L TPS, scroll through my article at the magazine: http://www.4wdmechan...leshooting.html.  You have some good scan tools.  Can they run a TPS voltage test like the DRB-III tool? 

 

I also hinted about an oscilloscope check of the ignition, the old and traditional way to see if there is really a #1 misfire or not—and pinpoint why...Check it out...

 

Moses



#51 bamafan1

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Posted 01 January 2014 - 02:13 PM

Thanks again for the input. I had read the post from 2008 and have considered replacing the TPS and CPS with Mopar components. As for the capabilities of the scan tools I can borrow, I honestly don't know. As soon as I do more checks I'll post it. Again, thanks for your time and suggestions. Will advise.



#52 Moses Ludel

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Posted 01 January 2014 - 03:59 PM

Unless your CPS was damaged from being loose, I would begin with the TPS switch. You can check the ohms-resistance on the CPS if you're concerned. I have specs if you need them, Bamafan1!

 

Moses



#53 bamafan1

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Posted 01 January 2014 - 05:11 PM

Well, I was going to do the TPS first then CPS. The only reason I mention the CPS too is that fact that it was loose nor know if it's the original or not. If it was replaced with an inferior product then who knows. As for any spec's I'll always be glad to get any info possible.



#54 Moses Ludel

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Posted 01 January 2014 - 07:42 PM

A footnote on the CPS: The stick shift models have a conventional sensor with a pre-set depth on the probe/pickup. Automatic transmission models use an adjustable pickup (single bolt unless 2.5L, which uses two nuts instead of bolts) that requires a paper gap and fresh start-up depth for the sensor pickup. The gap is established using Mopar part #05252229 paper spacer for initial depth setting. The paper spacer tears off as the drive plate rotates.

 

The CPS and notches on the flywheel or drive plate are essentially a hall effect switch with sync and signal generator phases. Again, proper pickup gap is important on automatic transmission applications, if too close, the pickup will be damaged as the engine cranks. If you have a manual transmission, the CPS pickup depth does not require adjustment.

 

My Mopar manuals simply say that the CPS should be tested with the DRB-III scan tool or to refer to the "Powertrain Diagnostics Manual". Essentially, this magnetic core sensor pickup either works or doesn't work. If mounted correctly, with the right pickup depth, the CPS should work—or not, in which case you will get a MIL, even with just engine cranking.  That's the test...Unless the CPS probe is physically damaged, it should work.

 

Moses



#55 bamafan1

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Posted 01 January 2014 - 07:58 PM

I've got a manual transmission. Is it safe to assume the CPS would have a separate code? I'm assuming it's functioning properly, but I'm not sure what, if anything, the previous owner may or may not have replaced. I've decided that I'll try a new TPS and ask if I can return the CPS if unused/uninstalled. At least that way I can compare what I've got vs. what should be.

#56 Moses Ludel

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Posted 02 January 2014 - 12:47 PM

"No Crank Reference Signal" is a Code #28.  This would be the CKP or CPS signal during engine cranking, so yes, there is a distinct code.  Code P1398 is a "No Crank Sensor Learn" code.  Both would be indications of a possible crankshaft position sensor fault.  If you try the TPS by itself, first, you can separate the issues and pinpoint the possible cause of trouble.  That, of course, is if the P0301 DTC decides to go away!

 

When you install the TPS, be careful about winding tension to the normal baseline position.  Use care, you'll see the relationship of the parts.  Let's see what this does.  If nothing else, you're replacing an obvious wear item in the EFI/MPI fuel and spark management system, and that's useful.

 

Moses



#57 belvedere

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Posted 03 January 2014 - 05:03 AM

I don't see where you mentioned the year of your Jeep, so this may or may not be relevant.  I have a '98 XJ with the 4.0.  When I bought it, it had a slightly rough idle.  No biggie, a good tune-up will take care of it.  Over the next couple weeks, I pulled my hair out as everything I checked failed to reveal the cause of the P0301.  At my wits end, I stumbled across a TSB that covered, I believe, '96-'99 4.0s.  It said that if you had a misfire and all other possibilities had been eliminated, you are to run Mopar Combustion Chamber Cleaner and replace all the valve springs.  (I suppose a weak spring could cause the misfire, plus allow carbon buildup, therefore requiring the CCC).  I ran the CCC and replaced the springs on just cyl 1.  Problem solved!  Again, this might not be your problem, but just wanted to throw it out there.



#58 bamafan1

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Posted 03 January 2014 - 05:15 AM

It's a '98 with a 4.0, manual. I have Seafoamed but not used Mopar product. As for the valve spring, I considered that based upon some advice and forums. However, idle doesn't seem rough (rpm's are constant when sitting still). Also, I've been lead to believe I'd hear noise too. How difficult is it to replace a valve spring?

#59 belvedere

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Posted 03 January 2014 - 05:35 AM

There wasn't any unusual noise, but I did have a slightly rough idle.  I used the old "rope method" (moved the piston down, slowly stuffed a new nylon rope into the spark plug hole, then turned the engine by hand until the piston was up as far as it could go).  Then I used a spring compressor that pivoted on the rocker arm stud.  A couple tips for replacing springs: replace the valve stem seal, and use a magnet to catch the keepers when you compress the spring and grease to hold them in place when re-assembling.



#60 bamafan1

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Posted 03 January 2014 - 05:52 AM

Thank you for info. Unfortunately, I'm not that experienced to do alone (nor do I have all the correct tools). Maybe I can find a video or step by step instructions. Again, thanks for the advice.

#61 Moses Ludel

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Posted 03 January 2014 - 08:10 AM

I'm pleased to see you jump into this, Belvedere, great suggestions!  Regarding weak valve springs, they can show up in a simple manifold vacuum check.  At any steady throttle setting, there will be an erratic, shaky vacuum needle movement with the vacuum gauge hooked up to an intake manifold vacuum source.  (Not to be confused with the wider swinging needle movement associated with a valve that is steadily leaking.)  As you share, Belvedere, weak valve springs can build up carbon, as the valves do not seat firmly when closed.

Attached File  Valve Spring Seating Pressure Tester.jpg   13.92KB   0 downloads

Valve springs can actually be tested for valve seat pressure on the engine.  Above is a photo of a simple tester available for that purpose.  (Click here for a more upscale Moroso 62388 design available at JEGS.)  With the rocker arm(s) removed, head and valves still in place, this over-the-top spring pressure tester can indicate the actual seating pressure, which is a true test of each valve spring's function.  This is a sensible testing method with the least amount of teardown work: simply removing the valve cover and rotating the crankshaft to close the valve(s) to be tested.  (Caution: Disconnect the negative battery cable to prevent starter engagement when turning the crankshaft by hand.)

 

There are two off-the-engine tests for weak valve springs.  If Belvedere still has the original springs, measuring and comparing the free standing height of the springs can be one test.  Another method, commonly used by automotive machine shops and race engine builders, is actual spring compression testing (read in actual pounds force or as PSI) with a special gauge.  This measures pressure as the spring compresses. 

 

As for removing the valve springs, Belvedere's method works.  So does an air hold, and this is especially easy for #1 cylinder, since the timing mark for TDC on the crankshaft damper is a quick way to find TDC for #1 piston. 

 

Here's how I do an AMC-design Jeep 4.2L or 4.0L valve spring removal:

 

1) Disconnect the battery negative cable to disable the starter.  Remove the valve cover and spark plugs, at least #1 plug in this case, all of them to make rotating the crankshaft easier by hand.  Rotate the crankshaft by the damper bolt, turning the crankshaft in its normal direction of rotation.  Watch the valves open and close to be sure #1 piston is coming up on its compression stroke as you bring the damper pulley around to TDC on the compression stroke.

 

2) Set the damper mark at TDC to be sure the #1 piston is at the top.  This will prevent fears of "losing" a valve into the cylinder.

 

3) Use an air hold fitting in the #1 spark plug hole to keep the valves up in position.  These adapter/tools are commercially available and inexpensive, or you can make an air hold tool with an air coupler and an old spark plug.  (See my comments below.  Summit Racing lists the KD 901 adapters for $4.97, the best price I've seen anywhere!  For that price, no need to make your own.)

 

4) Remove the #1 cylinder intake and exhaust rocker arms.  The pedestal bolts simply get torqued back into place, there is no valve "adjustment" to be concerned about when you reassemble the rockers.  (Just align the arms carefully with the pushrod tips and valve stems when you reinstall the rocker arms.)

 

5) With a stream of air applying pressure from any reasonable size home shop or garage air compressor, you can remove the valve springs using the "over the top" method.  (80-90 PSI should be plenty, there will be some leak down, so your tank compressor should be full when you begin the spring change out.  You can recharge the compressor if necessary between each spring removal.)  Belvedere's approach with a pry tool attached to the rocker stud can be effective, and this tool is readily available.  KD has made an affordable rocker pedestal pry bar for many years.  Even if "universal" fit, however, make sure the tool is designed for the Jeep 4.0L engine application, or you will be fighting this task.

 

6) There is also an over-the-top valve spring compressor available, which can be easier to control for the less practiced mechanic.  (OTC's version is shown at the Summit Racing page link.  KD makes a tool like this, too.)  This is a two jaw compressor that can compress the spring between the valve spring retainer and the spring coils.  This tool is great—as long as there is enough installed spring height and adequate coil gaps for the jaws to fit.  You must be able to compress the spring enough to safely remove the valve keepers.  With either tool, stay centered on the valve spring retainer to prevent valve stem or keeper damage, and carefully remove the keepers like Belvedere cautions.  Belvedere's magnet suggestion works.

 

As a valve hold, Belvedere's traditional rope method certainly would work.  (I like that vintage Mopar logo, Belvedere!)  Make sure the piston is coming up on the compression stroke before inserting the rope.  Otherwise, rope could get caught between a valve head and seat, which would reduce exposed valve stem height (or chew up the rope under valve spring pressure).

Attached File  Cylinder Leak Down Test-7.JPG   97.49KB   0 downloads

As for making an air hold tool, above is a photo of the hold I made in ten minutes for a tight-access Honda four-valve motorcycle engine.  The KD type adapter is so inexpensive that unless you need the tool this minute or have a unique situation (like the narrow access Honda four-valve thumper motorcycle engine, which will not accommodate the air hold adapter!), buy the KD or similar air adapters.  

 

Steps involved in making and using an air hold tool:

 

1) Remove the ground strap from the old spark plug shell.

 

2) Knock the porcelain and center electrode out of the plug shell.  Use eye protection, you're breaking porcelain/glass here.

 

3) If the shell size allows for tapping with a pipe tap, you can drill, cut and thread for an air coupler fitting's male threads. 

 

4) Use Teflon tape on threads of the air coupler fitting if you do use the threaded method.  I find brazing works very well and can be a much quicker way to attach the air coupler fitting—if you have an oxy-acetylene welding/brazing torch. 

 

5) Surface grind away any rough areas, like the remainder of the ground strap weld.  Wire brush your "new tool" as required.  You don't want loose material to blow into the engine's cylinder.

 

6) Thread your KD type or homemade tool into the spark plug hole. With the piston at TDC and the valves closed, hook your hose coupler to the air fitting and apply compressed air at the fitting and into the cylinder.

 

The air hold tool is a way to hold the valves in position and also run a crude cylinder leak down test.  (For details on a leak down test, see my HD video how-to at the magazine site.)  Though you cannot measure the percentage of leak with an air hold adapter, you can certainly find a badly leaking valve or leaky piston rings by the volume of air leaking out of the cylinder through the exhaust pipe, intake manifold/throttle body/carburetor or into the crankcase.  The leak down test is only reliable when performed with each piston at TDC on its compression stroke and both valves closed.

 

That the PCM would send a #1 Cylinder Misfire DTC, code P0301 in this case, due to weak valve springs is "interesting". The diagnostic tie-in here would be incomplete combustion, since fuel flow volume through the injectors is uniform (whether the valves seat properly or not), and the ignition spark reliability can be easily determined with an oscilloscope analysis.  Poor injector flow or weak spark can also create incomplete combustion and a misfire.

 

So, that means that the DTC reflects poor combustion at #1 cylinder, which could also be the result of inadequate valve sealing from the weak springs.  AMC-design engines do not have a history of weak valve springs, so weak valve springs should not be an epidemic or wide-ranging concern.  However, it would be a factor in some cases, and "weak valve springs" can result from valve seat recession/wear, overheated valve springs or over-revving the engine to the extreme and "floating the valves".  The 4.0L and 2.5L engines are known to run 250K miles without valve spring issues.

 

Belvedere, thanks for sharing.  This kind of information is very helpful to the forum members!  I'm very pleased that you take time to contribute at this level!

 

Moses


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#62 belvedere

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Posted 03 January 2014 - 08:44 PM

Great write-up, Moses, with lots of explanation/details.  I like your instructions for the home-made air adapter!

 

It was interesting reading about the tool designed to test valve springs on the engine...I hadn't seen those before.  I was going to take the springs to my local machinist to test, just out of curiosity, but never got around to it.  Maybe I will yet.

 

Like I said, according to the TSB, this applies only to a few model years.  I wonder if Chrysler had changed the valve spring design for some reason, or the supplier was different, or ???

 

My understanding of the PCM detecting the misfire is that it uses the CPS to detect a change in the momentum, or speed, of the rotation, and also, depending on when in the rotation this happens, can detect which cyl is causing it.  (I hope I didn't make that too confusing or unclear!)  Honestly, I can't remember where I got that info...hopefully I read it somewhere, and didn't just dream it up!  ;)

 

Jeff



#63 Moses Ludel

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Posted 04 January 2014 - 11:36 AM

Thanks, Jeff...Interesting comments about the CPS function. This is a hall effect system and is fairly straightforward. The notches in the flywheel or flexplate and the pickup provide a precise location for the #1 cylinder TDC position (actually the pulse output is 4-degrees BTDC on the 4.0L and the PCM calculates TDC from this generated signal).  The rotating, notched flywheel/flexplate and the magnet in the CPS probe generate the pulse signal. 

 

Mopar defines the CPS function as:

 

"This sensor is used to indicate to the [PCM] that a spark and or fuel injection event is to be required. The output from this sensor, in conjunction with the camshaft position sensor signal, is used to differentiate between the fuel injection and spark events. It is also used to synchronize the fuel injectors with their respective cylinders..."

 

The CPS would help the PCM sense minute fluctuations of speed caused by a misfire. Why the constant reference to #1 Cylinder on bamafan1's engine is interesting. While fluctuation could be caused by a misfire at any cylinder, there seems to be an epidemic of #1 Cylinder Misfire codes out there, suggesting something other than a local (#1 cylinder only) misfire.  

 

If this code is always valid and really does include weak valve springs at #1 cylinder, as in your experience, the only thing I can add is that #1 cylinder is usually the hottest running cylinder in an inline six. That could fatigue the valve springs earlier on #1 than other cylinders. We can test and confirm this with a simple surface thermometer, comparing #1 cylinder's temperature to the other cylinders with the engine hot. A good place to probe heat would be the cylinder head surface at the spark plug areas or the upper cylinder and head mating areas. Let's see what comes up! 

 

Regardless of how the PCM determines a misfire, the cause of a true misfire (not just a false signal) would be mechanical. In my view and experience, this could be caused by a variety of factors, here are a few quick prospects:

 

1) Ignition malfunction including spark wire breakdown, corroded rotor tip or distributor cap contact resistance

2) A lean or rich fuel mixture, more likely lean in the case of electronic fuel injection, especially multi-point MPI with an injector for each cylinder (much easier to determine air/fuel ratio per cylinder than with a carburetor or TBI, which feeds all cylinders through an intake plenum)

3) Low compression, which could be caused by poor ring seal or leaky valves

4) Ineffective or erratic spark timing advance, which could involve several sensor signals like the MAP, coolant temp, intake air temp or mass air flow in a MAF system

5) Vacuum leaks at hoses or the intake manifold junction with the head—good idea to re-torque the intake manifold, we haven't done that yet! 

6) Exhaust gas recirculation valve issues: EGR unseated, sticky, fluctuating, fluttering, take your pick.

7) Oxygen sensor or catalytic converter issues, or a restricted exhaust system

8) Crankcase ventilation issues in a PCV system

9) Out of sync crankshaft and camshaft position sensors (worn timing chain, distributor installed improperly, distributor timing position off). This could send a camshaft position sensor fault code, or maybe not if the issue is tottering.

 

The borderline camshaft/crankshaft sync problem could be a loose timing chain issue. This would not be surprising for higher mileage engines. If forum members are curious, I can suggest a quick test that I've used for years to measure timing chain wear. The method is accurate enough to rule out a major problem with the chain.

 

Each of these misfire sources has its cause, and we can drill down to confirm. I like to find actual problems, and I'm sure bamafan1 would like to see his MIL light go out. We'll keep after this...

 

Moses



#64 bamafan1

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Posted 04 January 2014 - 11:57 AM

Just a brief note I don't think I mentioned previously. When the mechanic and I were doing the various checks (compression, intake manifold leak, swapped injectors, etc.) we originally pulled #1 & #2 plugs. #1 was not warm, but sparked fine. #2 was warm, not impossible to hold, but warm enough. I haven't replaced the $120 Mopar TPS yet because of the recent valve spring conversation. I don't want to waste $120 by installing it as I'll need that $$ to have the valve spring replaced. Unfortunately, due to my lack of engine knowledge and tools I'm probably going to have to take this to a dealer to finish diagnose. Any idea what that might cost?

#65 Moses Ludel

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Posted 05 January 2014 - 10:23 AM

Like your idea of sparing the $120 for a new TPS, bamafan1. As a alternative, the Auto Zone version (purchased on a weekend when Mopar parts were unavailable) was a fraction of this pricing and has work well to date.

 

The cooler #1 spark plug could be revealing, bamafan1!  What was the cranking compression on #1 cylinder? A colder plug (un-fouled and still firing) is not a good sign, usually indicating low compression or incomplete combustion.  It can also indicate an fuel air-fuel mixture error, typically running rich, which has a cooling effect unless the plug actually reaches the point of fouling out. A fouling plug is equivalent to retarding the spark timing. With low compression or poor cylinder seal (including the weak valve spring possibility with the engine running), modern engines can still clean off a spark plug due to the high spark voltages available.

 

Worth noting, the traditional oscilloscope engine analyzer's spark firing test is very valuable. The scope's ability to assess each cylinder's relative compression and its combustion pattern can be revealing. When you replace all of the ignition parts (even more parts if we follow the OBD-II DTCs!) and still have a cooler plug, this could appear as a weak cylinder firing line with the engine running. Differences in spark plug firing line height, especially after installing fresh tune parts like you have already done, can reflect variations in the combustion efficiency between cylinders!

Attached File  Sun 720 Analyzer.JPG   93.01KB   0 downloads Attached File  Sun 720 Analyzer-2.JPG   91.64KB   0 downloads Attached File  Sun 720 Analyzer-3.JPG   113.53KB   0 downloads Attached File  Sun 720 Analyzer-4.JPG   98.63KB   0 downloads Attached File  Sun 720 Analyzer-5.JPG   94.52KB   0 downloads

Scopes like my vintage Sun 720 will even perform a "dynamic compression check", shorting out each plug wire (engine at an idle) and comparing the drop in engine rpm as each cylinder goes off line. (This might be more difficult with an MPI engine designed to compensate and restore the idle rpm. There should still be a momentary rpm drop before the idle air control kicks into play.) Eliminating spark to a low compression (or poor combustion) cylinder will barely change the engine's idle rpm. 

 

Also, simply "blipping the throttle" while reading the spark firing lines on an oscilloscope analyzer will show firing line changes (i.e., compression irregularities) as the engine load increases. On a scope, throttle "snapping" is a realistic test for low compression because it takes into account the engine load. This test quickly turns up weak valve springs, too, as a quick speed change will exaggerate the valve spring issue.

 

Note: Jeff (Belvedere) is likely onto this one...We used to idle the engine and pull individual spark wires with an insulated spark wire pliers (at each plug wire's insulator to prevent damaging the wire!), noting the rpm drop on a tachometer. This is essentially the same test as the scope's "dynamic compression test" though not as sophisticated. (Again, the Idle Air Control function on EFI/MPI makes this test more challenging.) If a given cylinder, like #1 in this case, shows little or no rpm drop, there's either low compression, a limited fuel supply (with MPI) or poor combustion.

 

Is this time for a leak down test or at least an "air hold adapter" test at #1 cylinder? The $4.97 adapter and 80-90 PSI of compressed air into the cylinder at TDC on the compression stroke could suffice as a quick leak check. (No percentage reading, of course, but if there's a substantial compression loss/air leak, you'll find it quickly!) A quick interpretation of air leakage would be:

 

1) Leaky intake valve will be audible at the intake. Open the throttle to hear the air leak better.

2) Air exiting the tailpipe is a leaking exhaust valve.

3) Air entering the crankcase would be audible by simply removing the oil fill cap. This air leakage would be blowing past the piston rings.

4) A compression/air leak loss between two adjacent cylinders is typically a blown head gasket. Bubbles in the cooling system can also be a blown head gasket (into the water jacket). Warning: If you suspect a leak between the cylinder combustion chamber and the engine's cooling ports, drop the air apply pressure to below 20 PSI—or you could damage the radiator or blow off the radiator and heater hoses!

 

If you have an air compressor, optimally with an air tank, this quick air leak test with #1 piston at TDC on the compression stroke might help demystify the #1 cylinder's condition and firing capability. A limitation is the static engine not spinning or changing speeds. A running engine is a better check for weak valve springs.

 

OBD-II and handheld diagnostic scan tools are now the alternative to traditional diagnostics methods. OBD-II DTCs, as we've discovered in this ongoing #1 Cylinder Misfire P0301 chase on the Jeep 4.0L engines, are not failsafe. By contrast, the once popular Sun 720 engine oscilloscope analyzer featured a vacuum gauge, timing light with built-in advance, leak down tester, combustion analyzer with A/F meter and other tools, each mainstays for pinpoint engine diagnostics.

 

Unfortunately, most vintage oscilloscope engine analyzers like the Sun 720, which featured a wide array of functions in one machine, have been sold off to vintage car museums as memorabilia! As you would suspect, I've kept my late 'sixties "muscle car era" Sun 720 machine...

 

Moses



#66 bamafan1

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Posted 05 January 2014 - 10:51 AM

I bought the Mopar TPS in lieu of "aftermarket" because of the general sensitivity of the 4.0. As for the coolness of plug #1 as testing proceeded it did eventually warm up. When we checked compression we did it on #1 & #2 only. #1 was between 120-125psi, #2 was between 130-135psi. According to Mitchell1's website, compression should be 120-150 (discovered that after compression test). As for head gasket, I don't think that's the issue. Radiator is full as is reservoir and neither have been touched since I took ownership 27 months ago. So, all that being said, I'm back to my original dilemma: I don't have knowledge or tools to continue on my own and am concerned if I take it to a shop or dealer I'll spend unnecessary $$.

#67 Moses Ludel

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Posted 05 January 2014 - 12:31 PM

I would rule out the head gasket, too, Bamafan1. If the gasket were leaking between cylinders, you'd have very low compression in both #1 and #2.  If leaking from #1 into a cooling port, you'd have both a loss of coolant and an over-pressurized cooling system.

 

120-125 cranking PSI is not exceptional for a 4.0L.  Before borrowing trouble here, and to save you every expense we can, you might try my inexpensive tests, offered in the last few exchanges.  In particular, if you do have an air compressor, even a home garage variety for airing tires, try the cylinder leakage test, at #1 cylinder/TDC compression stroke, with the $5 adapter. A manifold vacuum test with a simple vacuum gauge might also prove revealing.

 

What you generally want in any engine is no more than 10% variation between the highest and lowest cylinders' cranking compression.  Following this logic, if #2 were 135 PSI and #1 is 120 PSI cranking compression, that in itself could be a difference tottering near 10%.  If your higher cylinders were, say, 140-145, with #1 at 120-125 PSI, that would be enough for the engine to run roughly, maybe even send a #1 Cylinder Misfire DTC. A 25 PSI variance has always been considered a problem for both tuning and delivering good performance.

 

We may be looking at that kind of cause here, in which case, I have a simpler suggestion. If the engine has decent oil pressure, does not burn excessive oil, has reasonable power, and is maintaining sufficient fuel efficiency, let this go for now.  To troubleshoot a tuning or fuel-and-spark issue on any engine presumes that the engine is in good condition at the onset.  I have four criteria that work for me before looking for tuning problems:

 

1) Normal oil pressure (good bearing clearances, oil pump, etc.)

2) Normal compression and cylinder seal (piston rings, valves, head gasket, etc.)

3) Normal valve timing (good timing chain and sprockets, etc.)

4) Normal valve lift (camshaft lobes normal, lifters holding and not bleeding down, etc.)

 

If any of these factors are not right, then tuning or cancelling a DTC like the #1 Cylinder Misfire will be a tail chase. 

 

Your engine in stock form approaches 9:1 compression (8.7:1 on paper, without carbon buildup).  To put that into cranking compression terms, an engine with 8.7:1 to 9:1 compression and a stock camshaft profile would have a cranking pressure in the neighborhood of 155-160 PSI.  According to Mopar, you should pick this pressure up within "three revolutions" of the crankshaft, not after cranking each cylinder for 10 seconds or more!  (Either remove all the spark plugs or disconnect the coil lead from the distributor cap to prevent the engine from starting!)  Make sure the throttle is open to admit a full air charge as you crank.

 

Be aware that the listed cranking compression in shop manuals generally follows the engine's OEM standards.  The Mopar manuals typically reflect "acceptable compression" for engine warranty purposes.  This also applies to "normal" oil consumption, where most engines of a given type might use little or no oil between 5,000 mile change intervals, but for warranty claim reasons, it's "acceptable" to use a quart of oil in 2000 miles or whatever. 

 

It is always assumed that a difference of 25 PSI between the highest and lowest cylinder is an engine running unevenly.  This could easily translate through the PCM as, like Belvedere suggests, a "misfire" at the weak cylinder.

 

I wouldn't lose sleep over this redundant P0301 DTC in your case. As long as your Jeep 4.0L engine is running okay, it's money in the bank.  I would not rush off to remedy the problem until you are ready to rebuild the engine, if you ever do.  We can continue to kick the P0301 DTC around, I'm pleased to do so, but if the cranking compression is 120 PSI on #1 cylinder, I'm suspect that we'll not make a lot of headway.  And as long as the Jeep is reliable, let's be happy that you're not spending needless money on it.

 

If my hunch is correct, you will likely find a high percentage of cylinder leakage at #1 cylinder. This can seem alarming, even justification for rebuilding the engine—and it often is. If the cause is "just" carbon buildup, the Seafoam fix or a similar remedy can sometimes be a "cure", at least short term. Carbon buildup is seldom an isolated event, though. There is generally valve, ring and cylinder wear, too. Actual mechanical wear or damage cannot be remedied by de-carbonizing the combustion chambers and valves with a cleaning agent or method.

 

It's also worth noting that some engines maintain functional cranking compression and run reasonably well despite showing a high percentage of cylinder leak down. These engines can go many miles without creating a problem, and they cost no more to rebuild later than now. Again, it goes back to the four basic engine needs and whether each need is sufficiently met—at least enough to postpone a costly engine rebuild.

 

Note: My approach with these posts is to not spend others' money needlessly. Sometimes, we're postponing the inevitable. This Jeep 4.0L #1 Cylinder Misfire P0301 DTC is a case where we need to confirm the engine's basic condition before attempting to "tune out" the problem. Our troubleshooting, in any case, needs to begin with confirming the four basics. Once we know the engine's basic "long block" condition, the rest is either chasing vacuum leaks, tuning or replacing defective parts that the PCM or an OBD-II scan tool might—or might not—turn up.

 

Moses



#68 bamafan1

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Posted 05 January 2014 - 01:56 PM

Moses, please note that I do not nor have felt that any suggestions were provided by you or anyone else to just spend $$. As for your criteria I think #1 and #2 (of your criteria) are good. Oil gauge has held same position since day one. #2 I think is good to based upon earlier check. That being said, unfortunately I don't have the skills, knowledge, or tools to confirm or deny #3 or #4. Any chance you could come to Alabama and instruct me in person? (just kidding, as I realize that's not feasible)

#69 Moses Ludel

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Posted 05 January 2014 - 10:30 PM

Just clarifying, bamafan1, there's always the "throwing good money after bad syndrome", and we don't want to waste money on tune parts when the engine is worn significantly. If we begin with the four engine basics, we can determine whether the engine is in "tune-able" condition. This #1 Cylinder Misfire code could border between a tuning issue and engine wear. Lower compression and compression variation between the highest and lowest cylinders might trigger this DTC code. Engine wear needs to be considered.

 

As for the #3 and #4 (valve timing and valve lift) basic engine needs, there are simpler rough tests for these two concerns. First, if you have an engine with timing chain wear, the valve timing is retarded.  So, assuming that the timing is not bad enough to have the chain jump a tooth, we can make a rough determination of whether the valve timing is retarded much.  Here's the quickest check possible:

 

1) Battery negative cable disconnected to disable the starter and ignition, note the #1 plug wire position on the distributor cap and remove the distributor cap.

2) Rotate the crankshaft in the normal direction of rotation and slowly approach the TDC mark on the compression/firing stroke. The rotor will be pointing toward #1 plug wire position when you stop at the TDC mark on the crankshaft damper. 

3) Now, very carefully watch the rotor as you slowly rotate the crankshaft in the opposite direction of rotation.  Note the exact point where the rotor begins to move.

4) At the outside diameter of the damper, measure how far you have rotated the crankshaft pulley/damper.  (Try to estimate the number of degrees based upon the degree marks on the damper.)  If you measure 3/4" or more of outer pulley movement before the rotor begins to move, on a pulley of this diameter, there's a lot of play in the timing chain and sprockets. 

 

Note: This is not a pinpoint test for chain and sprocket wear, but without removing the timing cover, this will provide a rough idea of whether the chain is too loose. If so, the valve timing is retarded. On an OBD-II system with both a crankshaft and a camshaft position sensor, there is a built-in check for the sync between these two readings. Theoretically, if the valve timing is too lagging, the camshaft position will be out of sync with the crankshaft position. A DTC should appear...if so, a loose timing chain could be at fault.

 

As for the valve lift, this is a bit more involved, as you need to remove the valve cover, and you need a dial indicator with magnetic stand:

 

1) Remove the valve cover and rotate the crankshaft with a socket and ratchet as you did for valve timing, with the battery negative cable disconnected to prevent starter engagement.

2) Bring #1 piston to TDC on the firing stroke (easy to determine as the valves will both be closed as the piston rises).

3) Set up the dial indicator plunger above the #1 exhaust valve's pushrod and rotate the crankshaft slowly to reach the highest valve opening point. If you have measured directly above the pushrod, you are measuring the lifter or camshaft lobe lift

4) This measurement indicates how much the camshaft lobe has raised the pushrod. Actual valve lift is similar, you measure at the rocker arm directly above the valve stem. Valve lift takes into account the rocker arm pivot ratio.

 

If you want the valve lift test to be more accurate, measure the actual valve opening in 1000ths of an inch of valve lift. Compare this with the camshaft and rocker arm lift specified for a stock Jeep camshaft. (I can provide a figure if you do this test.) You can check and compare the lift at each of the twelve valves, measuring from a closed position to a fully opened valve. 

 

The concern here is whether a valve lifter is badly worn (you'd likely hear it as valve clatter) or a camshaft lobe(s) are flat. Jeep 4.0L camshafts and lifters do not have a bad record in terms of lobe and lifter wear.  Many engines do, though, including a large number of small- and big-block Chevrolet V-8 engines "in the day" that had OE camshaft lobes go flat from poor billet material. Typically, a Jeep camshaft and lifters get replaced on a higher mileage engine during a rebuild. The chain and sprockets always get replaced.

 

I would not be as concerned about the valve lift, though it could create the misfire issue if lobes and lifters have significant wear. The timing chain is another story, though. Any Jeep 2.5L four or 4.0L and 4.2L inline six with higher mileage can use a new timing chain and sprockets. Again, unless this will make a significant change in overall engine performance or prevent a catastrophic event like an extremely loose timing chain jumping teeth and slamming the valves into the piston heads, wait until the engine rebuild to address a worn chain, sprockets or lifter/camshaft wear.

 

My first move at this point would be the cylinder leak down test performed on #1 cylinder with the piston at precisely TDC (highest ring and cylinder wall wear point in the cylinder) and the valves both closed (on the compression/firing stroke). Pinpoint the leakage, with 120-125 PSI cranking compression, there will be cylinder leakage. Also, I would check the manifold vacuum at an idle. Retarded valve timing, like retarded spark timing, will show up as low manifold vacuum readings at an idle.

 

Moses



#70 jj_jeep

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Posted 07 January 2014 - 05:41 PM

I've been following the thread with interest and thought I would offer a quick update on my Jeep... I get an occasional MIL for a cylinder 1 misfire, but I don't actually notice the misfire (if there truly is one) like I did when the bad injector was in there. And when the Jeep started at the end of the work day yesterday when it was -15 air temp, I feel pretty good about driving it for a while! it idles a little rough, but at 253k miles, I can accept that as long as it's not stalling (which it isn't).

#71 Moses Ludel

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Posted 07 January 2014 - 08:02 PM

Great to hear your update, JJ_Jeep!  Sounds like high mileage does play a role with the #1 Cylinder Misfire DTC.  We're back to basics, and I'm glad the discussion went full circle to addressing underlying engine condition and wear factors...DTCs are obviously more precise when equipment is newer.

 

Pleased that your Jeep starts at -15 F and your heater works!  I use a block heater below 40-degrees F as a means for keeping the engine bearings in good condition. 95% of engine bearing wear is at startup.  Keeping the crankcase warm helps offset startup wear—and the heater is functional within a few blocks of driving! 

 

You know, we're talking about vehicles with real use, and given the cost of a new replacement Jeep, or even a thorough engine rebuild or crate motor, every day we can drive these vehicles safely is money in our pocket—they can only depreciate so much and are most likely at or near their lowest price point by 150K or more miles. 

 

Our 1999 XJ Cherokee 4.0L 4WD has 145K miles and still runs very well and quite reliably.  (We bought it stone stock and in "good used condition" at 94K miles.)  It would be ridiculous to dump the XJ now, as these vehicles, maintained properly, can often reach 250K miles, like your TJ Wrangler, without a whimper. 

 

I'm grateful for my background as a professional mechanic and grateful for good mentors and broad based learning opportunities along the way.  Over the decades, it's saved our household a small fortune in vehicle expenses—and lost dollars in new vehicle depreciation, which can be substantial.

 

Happy to help keep the high-milers running safely and reliably...We'll focus on "reality checks" for openers and start our troubleshooting with a solid assessment of the engine's basic condition...

 

Thanks for sharing! 

 

Moses



#72 bamafan1

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Posted 25 January 2014 - 07:47 PM

I'm back with a dumb question. After driving my jeep if I remove the distributor cap should the rotor be near/pointing close where plug wire #1 connects to the distributor?



#73 Moses Ludel

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Posted 25 January 2014 - 09:08 PM

At these forums, there are no dumb questions, Bamafan1! 

 

On a four-stroke engine like your Jeep 4.0L, the distributor shaft and rotor turn at 1/2 the speed of the crankshaft.  When the distributor shaft and rotor are set in position properly, the #1 piston will be at top-dead-center (the firing position) when the rotor points toward the #1 spark wire in the distributor cap.

 

As the crankshaft turns, so does the rotor.  The rotor, turning at 1/2 the speed of the crankshaft, will point to each cylinder's spark wire position only when that cylinder's piston is up to fire. 

 

The timing mark on the crankshaft pulley damper helps us set the rotor position for #1 cylinder's piston up to fire.  Important to note, the cylinder opposite #1 in the firing order (#6 cylinder for your 4.0L inline six, will also align to fire with the damper mark at TDC.  If you have the cylinder head off, you will see that when #1 piston (cylinder at the front of the engine) is at the top of its cylinder, so is #6 piston (cylinder closest to firewall).  Your engine's firing order is 1-5-3-6-2-4 with #1 and #6 pistons moving up and down in sync. 

 

The rotor is driven by the distributor shaft; the distributor shaft drive gear is driven by teeth on the camshaft; the camshaft sprocket is driven by the timing chain; and the timing chain is driven by the keyed crankshaft sprocket.  When you shut off the engine, the rotor will be aimed in relationship to the position of the crankshaft and camshaft.  This could place the rotor in any of its 360-degrees of rotation.  The engine's crankshaft coasts to a stop somewhat randomly. 

 

If you want to know where the rotor should point for timing purposes, this position is always in relationship to #1 piston at top-dead-center ("0" degrees or TDC mark on the crankshaft pulley/damper) on its compression stroke.  A common error when timing a four-stroke engine is to set the crankshaft at TDC mark with #1 cylinder's piston at TDC on its exhaust stroke.  This would have #1 cylinder firing 180-degrees out of time at the distributor.  The engine will not run and usually backfires badly while cranking. 

 

Keep in mind, on a 4-stroke engine, the crankshaft turns two full revolutions for each one revolution of the distributor's rotor.

 

Trust this helps, Bamafan1...

 

Moses



#74 bamafan1

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Posted 01 February 2014 - 02:53 PM

Just out of curiosity, what should happen when you unplug the IAC. Not remove it, just disconnect it. Also, what is the part near the rear of the intake manifold, it sorta looks like a brass pipe plug? What should happen when you unplug it as well? Both questions are related to when the engine is running at idle.

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#75 Moses Ludel

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Posted 01 February 2014 - 07:14 PM

The IAC is the idle air control.  Disconnecting it should affect the engine idle speed.  A defective IAC shows up as an unstable idle speed, with the idle hunting up-and-down, unable to maintain a stable engine rpm.  The IAC in good operating order will maintain a steady idle speed, even as engine load changes.  This is why EFI engines are so well suited for rock crawling:  They don't stumble and stall as engine load increases unexpectedly, which occurs with a conventional carburetor.  With EFI/MPI, the idle air control needs to function properly.

 

The device in the picture looks like your IAT.  This is the idle air temperature sensor, which is part of the air-fuel and spark management system.  Idle air temp tells the computer (PCM) the actual temperature of incoming air.  This helps determine the fuel injector pulse width.  Pulse width determines the volume of fuel that flows through the injector.  Cold air during warm-up is an important signal, as is the coolant temperate (CTS).  Warmed up, the incoming air requires a different injector pulse width.  The IAT (intake air temperature) sensor is important.

 

Both the IAC and the IAT play important roles with engine fuel and air mixture settings.  The IAC adds just the right amount of air to a given fuel supply in order to maintain a specific idle rpm.  The IAT is a sensor that sends intake air temp signals to the PCM.  IAT signals give the PCM "information" required for properly regulating the injector pulse width and fuel flow.  The oxygen sensor (O2) reads actual oxygen content in the exhaust, after the combustion process.  This information is also very important for setting air-fuel ratios.

 

Moses



#76 bamafan1

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Posted 01 February 2014 - 08:59 PM

So if the engine is running and I disconnect the plug on the IAC and/or the IAT wouldn't that affect the engine and/or cause it to stall like it does when I disconnect the MAP? Would the IAC and IAT throw a code? When I disconnect either the IAC or the IAT there's no "reaction" by the engine nor do I get any code other than P0301.

#77 Moses Ludel

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Posted 02 February 2014 - 09:52 AM

Bamafan1...The IAC should throw a malfunction code P0505 if any of these conditions exist:

  • IAC motor connector is damaged (check connector and pins for damage, and moisture)
  • One or more IAC circuits open or shorted to ground
  • One or more IAC circuits are shorted to voltage
  • IAC has failed
  • PCM has failed

The IAT will throw a P1192 or P1193 code to share that the circuit is reading either high voltage or low voltage.  Most sensors can be readily tested with a quality digital volt-ohmmeter for proper continuity and ohms resistance readings.  Since temperature is usually involved, tests should be run with the right simulated temperature on the sensor to expose an "open" that may occur only when the sensor is warm/hot.

 

I poked around on the internet to see how folks now approach troubleshooting.  Of course it's impressive how troubleshooting can be helped along by self-interrogating electronics systems like the PCM's ability to troubleshoot and throw codes.  However, I also have experienced PCM issues where the PCM cannot interrogate its own problems and either fails to throw codes or throws them rampantly and indiscriminately with no real substance.

 

Weighing the popularity of this #1 Cylinder Misfire topic, I'm going to do a very basic troubleshooting HD video (maybe even a short how-to series) on quickly confirming the fuel, spark and timing functions of a modern Jeep MPI engine.  There's a tendency to either overthink problems or limit troubleshooting to a dependency on codes thrown by the PCM

 

Most important is whether the engine runs right or not...I'll help here...This is basic.  For a Jeep 4x4 used in the back country, you should be able to troubleshoot quickly on the spot.  Seldom do several "devices" fail at one time, and pinpointing the crippling trouble area can often be done readily.  We'll save the nitpicky, nuisance engine check light codes for when we get home—the idea is to get home.

 

Moses



#78 bamafan1

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Posted 02 February 2014 - 10:27 AM

Thank you for addressing the code question. However, if the engine is running and I unplug the IAC and/or IAT should the engine stall like it does when I unplug the MAP?

#79 bamafan1

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Posted 02 February 2014 - 12:14 PM

Another subject I'd like an opinion on is mpg, I run 33x10.50x15 BFG MT's (on it when I bought it). Mostly in town driving as far as street use goes and I checked mpg ob last tank and averaging 12.6 which seems significantly lower than average of 15 mpg. Just wondered if "misfire" is contributing to fuel consumption too?

#80 Moses Ludel

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Posted 02 February 2014 - 12:41 PM

Here's my take on your question, Bamafan1...At a stone steady idle, especially with a warm engine under no load, you may not notice the IAC function.  With the IAC plug disconnected, try setting the E-brake and place your transmission (manual?) in 2nd gear.  Keep your foot off the gas pedal and gradually let the clutch pedal up from the floor, just enough to create a load but not enough to stall the engine under normal conditions.

 

Normally, engine rpm will begin to drop then instantly attempt to stabilize toward the factory idle speed.  If the engine flatly lugs or dies, you'll get a sense for how a functioning IAC compensates for engine load to keep the idle speed stable.  (Normally, if you depress the clutch pedal when the engine has this load, the rpm will momentarily flare up.)  Obviously, if you let the peddle up too high with the brake set firmly, you will stall the engine.  We're talking about load, not a dead brake against the engine.

 

Unplugging the IAT of an idling engine, again not under load, would not make a noticeable difference—especially during cold warm-up where the CTS (coolant temp sensor) holds sway over the IAT function. 

 

Also, the IAT, even though it does have a role with injector pulse width settings by the PCM, is not as "important" as the O2 sensor.  If the upstream O2 sensor is defective, you'll always get an engine code and maybe limp mode at the same time!  (You'll get a code whether the up- or down-stream O2 sensor is defective, though the downstream should not throw the system into limp mode.)  The O2 sensor is the major player in air-fuel ratio settings and control of the injector fuel flow.  For emissions purposes, manufacturers are very concerned about the O2 function, and so is the EPA.

 

Again, if you suspect a sensor is defective, a quick ohms-resistance test of the sensor makes for quick troubleshooting.  We're trying to avoid unnecessary parts replacing...

 

Moses



#81 jj_jeep

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Posted 08 February 2014 - 03:43 PM

I haven't seen the MIL for a while now.  I am starting to wonder if it improved after I added coolant to the overflow bottle.  I noticed it was really low, so I filled it back to the full line.  Fortunately, it's been holding at the full line, so I don't seem to be consuming coolant.  And oddly, the MIL lamp has stayed away.  What's the likelihood that these two things are related?  Or is it just coincidence? 



#82 Moses Ludel

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Posted 08 February 2014 - 10:40 PM

If the radiator was also low, this could be an issue, possibly creating air blocks that could affect the coolant temperature sensor. The engine would likely be overheating by that point, though—maybe not in ultra-cold weather.  This is a longshot in any case...I believe some of the earlier work that we discussed has actually helped.

 

Your initial topic post has now generated substantial traffic, this is one of the longest threads at the forums and very popular.  Thanks for hitting a nerve, we've aired quite a few issues within the context of this #1 Cylinder Misfire code.  Exchanges have been thorough and thoughtful, you started it all!

 

Moses





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