carlosa

Hi Moses, Random misfire issue may be solved Sorry for my long absence, i`ve been very busy with work and parked the Jeep for the summer - I ran out of time to tinker with it and was afraid I might be hurting it even more. Your quoted post above had me thinking for a long time about the quality of the CPS. I had a premium Napa sensor in the Jeep after I pulled the transmission and fixed the flywheel bolts. This video came up recently, so I added it to my offline viewing list and watched it during an international flight. When I landed I decided to just take a risk and change a part... I ordered a new Mopar OEM sensor off of ebay. As far as I can tell it is identical to the Napa premium sensor, both are made in Mexico and both have the same general feel and quality. I put the new sensor in, took my time getting it snugged down tight against the spacer, and took it for a drive. Its now been 5 days of hard driving in first and second gear to keep the RPM's up, and I have had no re-occurrence of the random misfire codes. I have tried duplicating every scenario that previously would be a flashing light within seconds, and cannot. Engine braking down the hills here in the rain is much safer than riding the brakes on this Jeep and that alone is a bonus. Now I have a transmission issue, and some free time .. so i`d like to get back into some of the other posts we talked about. I may also try to build some sort of test rig to test and understand what goes wrong in these sensors, since it is a widespread problem. Otherwise, maybe I should invest in (hoard) Mopar sensors for the future.

Injector balance test results are in. For those not familiar: An injector balance test basically fires an injector a timed, specific number of times. You can then fire each injector and compare the results. Results are driven by the "leak down" PSI on the fuel rail. Each time you fire one, you re-prime the fuel rail and blow out unburned fuel, by cranking the engine. Ignition coil is unplugged during this scenario. The fuel rail was pressurized to basically 45 PSI by cranking a few revolutions using a hand crank button that links the battery to the starter solenoid. The pulser was set on 50 pulses, each 7 MS in length. #1: 33 PSI #2: 32 PSI #3: 32 PSI #4: 33 PSI #5: 33 PSI #6: 33 PSI So, these are not terrible. But it does indicate that 4 injectors are flowing less fuel in the same amount of time, as the other two. One of the 2 was replaced with a spare junk drawer injector, due to finding a crack. Next step: Replace the baskets on all 6, and repeat. If I find that they balance out better OR perhaps flow more fuel then that is good news! I don`t have any sort of specification on how much fuel they should flow under these conditions. If I see an improvement after changing the baskets, I may order a set of guaranteed quality rebuilt 4 hole Bosch injectors. I would not be doing this for any of the "perceived" benefits of upgrading to 4 hole, other than the fact that the price is similar, and they are not susceptible to cracking.

That is amazing, i`d love to find out exactly what it is inside the computer that fails. There arent any moving parts, so maybe a resister or continuity issue? Or a corrupted database table?

I have not eliminated the PCM at all. My approach is to test and eliminate the least invasive or easy access items, before moving on to more invasive or less easy to test items. So for example - the vacuum leak that you mentioned a few times is still high on my list, but I want to avoid tearing into that engine that far until I have eliminated everything else. The computer very well could be suspect. My auto enginuity won`t even connect to it. I have a solution for that as well that I will work on eventually. The situations where a PCM fails and needs to be replaced are very interesting to me. Interesting how it can sort of fail and still allow driveability. At the moment its a waiting game either for ordering tools, or for doing a few things then working, then doing a few more. I currently don`t have any budget restrictions on getting this fixed, so I will buy and test anything that I can get my hands on -- however without just "changing parts".

This topic is a fork off of my misfire diagnosis thread. I will be editing for easier reading and explaining all the various accesses we have for our DRB III era vehicles. In my opinion that proprietary tool is the biggest burden to a Jeep hobbyist. If anyone has any specific diagnostic tool requests, please post and I will go into depth about it! There are amazing tools available to GM guys and for that reason, many of us are wishing for a GM transplant. Aside from displaying misfire counts on a per cylinder basis, the smart phone apps along with a bluetooth OBDII transmitter will cover that vast majority of needs by anyone troubleshooting problems. The limitation in my case is the simple fact that I want to check if there is an occasional misfire at all times (idle or under load, normal driving, etc). As far as monitoring fuel trim and o2 sensor data, the app based setups are spot on. The minor issue there is the delay in update speed, although very slight it will sometimes show your o2 sensor staying high for 2-3 cycles then low for 2-3 cycles. As long as you understand the delay, you can account for that. WiTech/DRB from China There are Chinese knock off VCI pods that DO work with the DRB III emulator. I haven`t pulled the trigger yet, simply because it is using pirated software. If I don`t find a DRB III in the $1500 or less range, I will order the Chinese part and write up a full review of how to use it without pirated software (if possible) using the DRB III download from Controller Tech http://www.controllertech.com/drb-iii-emulator.html You do get WiTech with the Chinese systems and it is supported up until 2015 or so I believe. They give you the install CD then ask you not to go online, where the WiTech software would phone home and then disable itself. There are two styles - one is the VCI pod style that is corded and a separate unit, then there is the Micropod style that plugs directly into the OBD II space much like any normal bluetooth scan tool would. Starscan: I have talked with this seller on ebay in the past, and he says his system has a good working DRB III emulator built in. You might try contacting him to see if he offers an upgrade service. He seems to buy these devices, upgrades them, then resells them. He assured me that you will never have to subscribe to any service or do any future upgrades once it is ready to go. The only situation you may need to upgrade in the future, is if you change vehicles and want to support something new. In my opinion, having a starscan or drb iii that supports the generation of vehicles I have is good enough. http://www.ebay.com/itm/OEM-Chrysler-Jeep-Dodge-Sprinter-Starscan-Star-Scan-Dealer-Tool-DRB-3-/132197792408

Alright here is another little update with photos. I have tested various things over the past week, but haven`t had as much time to really work on it. That and i`m waiting on more tools to arrive to be able to test other things. I did a traditional compression test. Cylinders were from 148 to 160 PSI. Most were basically right in the middle at around 155. I pulled the injectors. Observed small amounts of rust inside the fuel rail, found one cracked injector - nothing leaking on the outside. Ordered new baskets. I pulled the one basket from the cracked injector and it was quite rusty and dirty but not sure its enough to affect the flow. By rusty I mean the nylon screen is orange rather than some shade of nylon. Replaced the one cracked injector with a spare I had Going to do an injector balance test before & after I change the screens. I just want to see if there is any flow issues so that I can see the difference. Likely will replace all with a rebuilt set, anyway. Did a fuel pump volume test. Spec is 1/4 liter per 7 seconds. I received quite a bit more than 1/4 liter as shown in a photo below. The manual specifies that the coil rail should reach 25 KV. I tried testing this by removing the rail, and hooking up a cheap spark test tool. It worked, but guessing where the spark fell on the gauge was kind of a joke. If I had to guess I would say it was right at the threshold or slightly below 25 KV on all cylinders. But, I tested two different coil rails with the same results. So for now i`ll rule that one out. Gauge is pictured. Have driven about 200 miles mixed city and freeway and have not had a light .. but I know if I push it and drive harder it will trigger. Still to come: Exhaust pressure test before/after cats, fuel injector balance test, locate a DRB III !!! I really want to see live misfire data, if any - and so far have not been able to recover that from any scanner I have. Auto Enginuity, Torque pro, OBD Link, etc.

So i`m not going to call this a resolution, but you got me thinking about that IAC. That is a hard device to bench test. I swapped in my throttle body from a 2001 XJ wholesale, with all sensors and everything and got this at idle (see attached image). I also beat on it a bit on the free way at all rpm ranges and could not get a flashing light. Idle is also very smooth. I have two concerns with calling this done: #1 - I reset the computer again for relearn. I may need to get several more trips in before I can really write it off as solved. The Jeep did run a little bit hotter than usual, hitting 200 degrees .. it has rarely if ever even hit 195. I would say this is a result of a much less than positive fuel trim aka richer condition due to a better stoichiometric ratio. There is also still a tiny bit more positive fuel trim than i`d like to see, but it is well within spec and has no wild swings into the 20's and 30's %. #2 - I can`t call it done until I devise a way to test the map, tps, and iac and see exactly what is going on with them that is out of spec. Obviously the IAC is not regulating air flow, as Moses mentioned several times in above posts. I did inspect the removed part and it is not gummed up with form a gasket, and besides .. this even happened long before I took it apart to clean it and reseal it. I will be posting again with photos and exactly what I find.

EDIT: Moses, you are going to end up being totally right about this being an air or vacuum leak. I tried again with the wd-40 today on a warm engine and could not manipulate the idle. So a tear down and inspection of the gasket and manifold will be in order. Remember that I also drove with all vacuum lines capped off at the intake. So i`ll pull the intake and exhaust manifold, check for cracks, and replace all gaskets next. The reason for this is .. I just hooked up the fuel gauge and see no real issues either at idle or at 2500 RPM. Pics attached. Thanks for all of this info. Its going to take me a few days to test everything and then I will report back. I will be doing a full series of testing on the fuel pump - from the flow capacity, pressure, voltage drop, etc. My gauge leaked again yesterday so I threaded the fitting back in with a thin layer of JB weld, i`m expecting it to be well cured and will test the pressure tomorrow both with key on, and with a direct 12v to the pump. I found that the replacement non-oem throttle valve cable is binding a bit, so just went and grabbed one from a 1997 ZJ that is silky smooth. Going to go ahead and attach a freeze frame from todays drive. This is after about an hour of varying speeds and I really had to push it to get the MIL to trigger. It went like this: Floored acceleration up to 80 mph, let off gas, coast down to about 60 mph, check engine light flashing during the entire coast down. Tapped the gas fairly hard and the light went solid. I am trying to find a copy of my scan software that will let me monitor misfires. I know the vast majority of them do not, but autotap and autoenginuity do.

Thank you for the detailed response. I have to say i`m very happy to hear from you. I have your Jeep book, and also have read many articles written by you for various magazines since the mid 90's. Rather than reply again inline, i`ll just address some of the points that are most pertinent to the current state of affairs. That may also make it easy to follow for others encountering this issue. DRB III Yes, quite expensive used on ebay - anywhere from $1200-2000. I consider it a necessary investment if I am going to have this Jeep for many years to come. There are chinese knock-offs that I have yet to test, but may depending if I can win an auction. Intake Manifold Leaks - I agree that the highest explanation for the positive fuel trim would be a vacuum leak. I have capped off all connectors and promptly reproduced the issue. I was careful to apply a minute layer of the aircraft sealant to ensure that it would not run or otherwise gum up the operation like RTV or silicone type sealants might. One thing that leads me to question the vacuum leak hypothesis is that the fuel trim stays almost exactly the same at higher RPM's. I have attached two screenshots demonstrating this - one is at idle, one is at 2500 RPM. I did test out WD-40 this morning with no noticeable change in idle, while monitoring the idle on my scanner. Exhaust causing fuel trim issues? This still leaves a potential exhaust leak that could be fooling the o2 sensors. I think it would be safe to go ahead and remove the intake and exhaust and reseal everything down to the collectors, while visually checking that the catalytic converters are in good shape. I just wanted to rule out pulling the head before doing this. Fuel pump/injectors causing fuel trim issues? I honestly have not looked at the injectors in any way during this adventure, simply because it runs so well at all times. I can never feel the misfire happening. I will swap in a spare set of injectors I have (that came with the fuel rail), after I clean them thoroughly. Will use all new o-rings. I obtained another fuel pump pressure gauge from Harbor Freight. The quality is lacking - but after opening up the guage and resoldering the fitting, it does not leak! So will test out the fuel pressure. I am aware of the fuel pump capacity test needing to reach 1/4 liter in 7 seconds, will do this as well. Yes, this is a coil on plug - distributorless engine. My original intent to obtain a DRB III was to test the cam position sensor alignment as part of my skepticism of the previous shops work. I don`t think this can cause a misfire anyway, so it has been moved further down the list. The fan is a thermostatically controlled system. Using the factory style clutch on what appears to be a brand new water pump. Head cracking - I haven`t seen any indication of a cracked head in the form of bubbles, residue, or anything else in the coolant - but I will send off a sample or engine oil and coolant to Blackstone to have it checked. I am hoping that this head is one of the later ones where the problems were solved. But, even if it is cracked, would this cause misfire readings on all cylinders as well as random misfire? Proper compression test - I can do this asap and report back. Again, thank you for accepting the challenges of this topic. I will absolutely report back any findings or eventual fixes that solve this problem. From my readings on many forums, either the problem is never solved - or the person never returns to post additional details. This does seem to be a common issue, and those who have reported solving it have done it in the most round about ways. Spending thousands of dollars on dealer labor replacing cats, head, etc. Then discovering that it was a faulty sensor.

2000 Jeep Wrangler TJ 32RH 170k Miles I bought this last fall with intentions of making it my forever Jeep since it replaces an identical one I had back when they were new. It had its engine replaced by a sketchy shop. I have been fixing things ever since. Some of the things I have fixed will be listed at the end of this post. In the interest of thoroughly understanding why this is happening and learning as much as possible, i`d like to keep this limited to diagnostics, testing, and troubleshooting rather than buying parts and bolting them on. I am well versed with the FSM, standard tools, and with Jeeps in general having owned everything from a CJ-5,7, XJ, WJ, YJ, TJ (twice). What I currently do not have is a DRB III - if anyone has one they`d like to sell please let me know. The problem: Random misfire flashing check engine light starting just over 3000 RPM and happening any time up to redline. Appears to happen more when cresting a long pass and then engine braking down the other side. Cannot feel any actual misfire. Over a long enough timeline codes will set for all 6 cylinders. No particular cylinder sets it off, but I tend to see p0306 earliest. Data includes fuel trim, TSB 09-003-03, vacuum, fuel pressure, and leak down test results: Fuel trim at idle is approximately 10% positive. And a snapshot at the time of the code being set is also usually around 10% positive. Photo attached shows the fuel trim at the time of a misfire, as you can see I floored it, light started flashing, and I took a screenshot, very simple. I have not replaced the intake manifold gasket yet, but have thoroughly checked all vacuum lines with propane, and brake cleaner. Have replaced a few that were suspect, but did not actually respond to propane. My understanding is even if this were an issue with the intake gasket, it should not affect under heavy load - but maybe when engine braking? For further proof of this, I capped off all vacuum lines at the manifold including the master cylinder, and was able to reproduce the error in first gear at 3100 rpm driving up my street. A vacuum meter (mityvac silverline) shows the needle bouncing/vibrating wildly at idle - but only within 1 or 2 marks on the gauge. This is indicative of leaking or worn valve guides? Vacuum test does not indicate exhaust restriction at any RPM level. TSB 09-003-03 - removed all rockers and verified a bullseye pattern is present. Did not rotate valves yet as I didn`t have a compressor available, and honestly I fully expected to be pulling the head during this process. Have run seafoam top end cleaner through the throttle body according to directions. Spark plugs are very clean and nice. Leak down test (cold engine): I have bad hearing, but could not hear or feel anything coming out of the throttle body, or the exhaust. No bubbles in the radiator. cylinder 6: set at 69, observed 62.5, percent difference: 9.88% cylinder 5: set at 70, observed 68, percent difference: 2.89% (was holding pressure by hand, cylinder may be lower in the bore than others) cylinder 4: set at 70, observed 64, percent difference: 8.95% cylinder 3: set at 69, observed 62, percent difference: 10.6% cylinder 2: set at 69, observed 60, percent difference: 13.9% cylinder 1: set at 69, observed 65, percent difference: 5.9% Fuel pressure: I had a crappy HF gauge but did not observe any negatives on fuel pressure at any RPM. I can retest if someone would like to see specifics. I did swap in a fuel rail with a shrader valve, this is one of the things that led me to believe the engine is a later model. Things that have been done - most of these are routine or were observed as being broken, missing, or neglected. I may have forgotten some but will update this list. 1. APP 985 plugs, removed AP985 plugs - this was done on day one. 2. Removed 180 degree thermostat, replaced with 195 - day one (the first time i drove it at the shop, didn't even have a thermostat in it) 3. Swapped in a known good coil rail from my XJ. No change whatsoever. 4. Built all new battery cables, soldered, marine heat shrink, direct cable from battery to body, and battery to block. ¹ 5. Swapped crank position sensor - not because it was suspect, but because it was BROKEN, and eventually did die causing a no start. I assumed the shop broke it when they installed the new motor. ² 6. Crank position sensor died again, 6 months later. ² 7. Correctly rerouted the belt, and installed a new one along with idler just because - this was done in the first month, did not observe any overheating or charging issues. 8. Fully disassembled and cleaned the throttle body. Noticed the IAC casting has been replaced and is not a good fit - so lapped all surfaces on a machinist surface plate, then reinstalled with aircraft form-a-gasket. No improvement, if anything the idle stays a little high at times. 9. Have done the disconnect, ground, reconnect, lights on, lights off thing at times just to force relearn (if that even worked on later models?) ¹ When doing the leak down test today I realized there is NO ground strap from the block to the head - will be repaired shortly. Edit: Added the strap, did nothing. See the last screenshot of current results. p0306 the first code to pop up this time. ² What I thought was top end noise all along was one of the four torque converter bolts riding around inside the tone ring of the flywheel. I dropped the trans to replace the flywheel thinking it was cracked, and discovered the bolt. Pic attached. Removed and inspected the flywheel, noted that it does not have the exact same tooth count or tone ring setup as the autozone replacement I bought, so reinstalled. It was in good shape anyway. Used ARP bolts to the torque converter, properly torqued. Also finally got the throttle valve cable perfectly adjusted, it needed an extra click on the tension side in order to shift properly. The bolt riding in there is what broke two crank position sensors - its amazing that they still worked for months with the magnet not even attached. Additional observations: I do not have proof but it almost feels like the misfire code is set at the same time the clutch fan is operating. In other words I can feel the sluggishness of the fan as well as some minor vibration at the time the light flashes. I am considering upgrading to a mishimoto electric fan and not because of current issues. I have noticed the ever so slight loss of coolant - where after 2 weeks or so it will be down to the top of the tubes when looking through the cap. It does not ever pull fluid from the reservoir, and has not dripped on the ground. Was able to pressurize the system and observe minor dripping from both hoses - going to write this off as solved. This is a 0331 TUPY head. The mileage, make, model of the engine are unknown - I am not entirely sure but it may have come from a WJ. I believe the date code reads 3 12 mx 17. Which is 2003-12-17