Moses Ludel

At our Jeep TJ Wrangler forum, we've been tackling the #1 Cylinder Misfire P0301 DTC issue. Member Belvedere brought up the weak valve spring issue and offered some great suggestions on changing out the valve springs on a Jeep inline six! Regarding weak valve springs on the 2.5L four or 4.0L and 4.2L inline Jeep six, weak springs 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 Belvedere shared, weak valve springs can build up carbon, as the valves do not seat firmly when closed. 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 classic rope-in-cylinder method works. (See the exchange at the Jeep Wrangler TJ forum under the #1 Cylinder Misfire thread.) 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 for lifting out and installing the keepers. Note: If you do use Belvedere's rope method for holding the valves, 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). 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

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. 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). 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

"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

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

Thanks for the intro, Jeff! "Belvedere" does say "Mopar" in a big way, this is a classic Plymouth moniker. I know the vintage and muscle era Mopar vehicles well, we'll have to get that Ramcharger into the Dodge/Ram Truck section here at the forums! Please jump-start the Ramcharger discussion topics... We all look forward to your participation...Enjoy the forums, your role is important to us! Moses

Alaska is very special from any angle, Belvedere...We'd like to do it with a travel trailer behind the Dodge Ram, noting where to park without attracting the bears...Would do the Okanagan Valley as we enter Canada, then travel up through the interior of B.C. to Dawson Creek, the Yukon, Whitehorse, Tok Junction and north to Denali...It's on our list, would like to make it before that changes to the "Bucket List"! Moses

Welcome to the forums, Belvedere! Like Biggman100, I really like Canada...I passed through B.C. and a portion of the Yukon on the way to Alaska in 1975, then spent time at B.C. during the launch of the Eco Challenge near Whistler in the 'nineties. Incredible country! A friend just shared this YouTube promotional video for the Province of Alberta: http://www.youtube.com/watch_popup?v=ThFCg0tBDck. Watch it in full-screen, high resolution. Watch this, you'll want to go there...Enjoy! Happy New Year! Moses

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

Well, if it's any consolation, here's a mirror of your problem at the Jeep Forum, dating to 2008: http://www.jeepforum.com/forum/f9/obd-ii-code-p0301-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.4wdmechanix.com/Jeep-Multi-Point-Injection-Operation-and-Troubleshooting.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

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

RareCj8...A leak down test is spot on and conclusive (see HD video for details). The damage source for my engine was clear when I discovered the 125 OEM main jet in place and dirt around the edge of the air filter. This cycle had been ridden primarily in Texas (lower elevations) on the lean mixture. Generally understood is that "uncorking" involves a list of changes, which includes the 175 main jet (selection is a no brainer, this is the OE main jet outside the U.S. for engines identical to ours). All of the XR650Rs with the OE main jet are under duress, especially non-California models still running with the original main jet. Uncorking without changing the main and pilot jets becomes the death knell. Here is the "official" Honda Power-Up Kit list of parts plus the removal of the air box restrictors. (This list is third party info and somewhat dated; confirm current part numbers available at your Honda dealership.) The list: 16211-MBN-640 (Insulator, Carburetor, which gets rid of the California "D" shaped restrictor manifold) 18317-MBN-640 (Exhaust Tip without the tiny outlet and restriction) 99105-MBN-0680 (68s Pilot Jet) 99101-357-1750 (Main Jet 175) 16012-MBN-641 (B53E Needle Set, this is based on tuning needs; at our altitude, try without the needle change first) Also expected is the removal of the "user removable" air box restrictions. A Power Up Kit should not be confused with the Honda Racing kit for the XR650R. The HRC kit adds a warmer camshaft, improved piston and rings with bumped compression (11:1, really?) plus other racing nuances. The OE Keihin pilot and main jet are each accessible with the float bowl removed, and the Keihin carburetor can be carefully rotated to access all four float bowl screws. They are Japanese Phillips head and vulnerable to rounding if not careful, but most of us who have owned Japanese motorcycles have been there and own a hand impact driver for that purpose. You can access and remove the main jet by simply unscrewing the drain plug at the bottom of the float bowl and accessing the jet with an appropriate 1/4" drive metric socket. This lean issue is serious enough to warrant looking at the installed jet if you're unsure of its size/flow. You and I live at nearly the same altitude, and I opted for a 172 main jet for the 4,500-7,000 foot elevation range that I typically ride. 175 would likely be okay if you want to play it safe for sea level, you should be able to readily run to 6,000 or so feet without fouling a spark plug. When you read the jet change charts, even from Honda, there's a wide range of adjustment for ambient temperature and altitude. My cycle's pilot had been changed to a 68 (not 68s), which I'll try and go from there. I haven't pursued the needle position or type, would bet it's stone stock since the carburetor's top looks unopened. We can discuss fine tuning and carburetor staging later...For others, keep in mind that tuning is altitude and temperature sensitive. As for the voltage meter(s) for the CJ-8 Jeep, I totally agree. We're back to my suggestion that you simply route the lead wire to the voltmeter through a standard Bosch-type relay that is key-on activated. The relay would close the circuit on the wire lead when you turn on the ignition key and open the circuit/lead when you turn off the key. This would deactivate current flow of any kind with the key off. Refer to my primitive drawing (earlier exchange) for ideas. Have a safe and very Happy New Year! We'll ride the Big Red Pigs (XR650s) at the desert when I get this beast plated, I'm looking forward to that prospect! Moses

The magazine recently purchased a 2000 Honda XR650R motorcycle with less than 1000 original miles on the bike. An honest and forthright previous owner could not start the engine, and given the mileage, we agreed that the problem was stale winter (ethanol) fuel—which had eaten up the plastic tank screen! I trailered the cycle home and looked forward to restoring the fuel system and completing the dual-sport conversion process. The motorcycle will be an HD video shooting platform for remote backcountry documentary filming and off-pavement event coverage, so the XR650R's low mileage seemed a huge asset. After 20 hours of prepping the cycle for a Nevada dual-sport inspection, including some minor tuning and checking out the bike's general condition, I discovered that the 650 thumper engine would not start. Consulting two friends with XR650Rs, I assumed that my starting technique was the culprit. A heavy cardio workout later, it was apparent that the compression was lacking. I did a quick compression gauge check and discovered a 95 PSI cranking compression issue. (To assure an accurate reading, make sure the auto-decompression mechanism is not holding the valves open when performing a compression test!) My next step was a cylinder leak down test, which I have covered in detail with an HD video how-to feature. All of this is covered in a series of HD videos available at my YouTube channel and the motorcycle Playlist. (Go to https://www.youtube.com/c/roadreadywithmosesludel and open the XR Honda motorcycle playlist.) The leak down test pinpointed leaking intake and exhaust valves; a look inside the cylinder (through the spark plug hole) also indicated scoring at the upper wall of the Nikasil cylinder plating. Time for an upper engine tear down, which I cover as a step-by-step HD video at the YouTube Playlist. So, how did a "bulletproof" Honda XR650R motorcycle, with less than 1000 miles since new, end up with a worn out set of valves and leaky piston and rings? The answer is two-fold: 1) the motorcycle had an incomplete "uncorking" job with a partial "Honda Power-Up Kit" installed and 2) a leaking aftermarket air filter had seeped abrasive dirt into the air stream and through the engine's intake system. The air filter issue is notorious for pitting valves, scoring an upper cylinder and damaging piston rings on motorcycle and automotive engines. An incomplete uncorking calls attention to an ever important problem for any motorcycle engine modification: the need to re-jet the carburetor to compensate for improved intake flow or a less restrictive exhaust system! The "Power-Up Kit" opened up the exhaust cap on the muffler and reduced exhaust backpressure (basically an HRC end cap). The cycle is a non-California model, so there was no restrictive "D" molding in the intake manifold grommet. (The non-California intake manifold is considered the unrestricted air intake, often sold as the upgrade for better breathing.) The pilot jet had the Power Up Kit's #68 sizing, though not the specific "68s" style. However, for some unfathomable reason, the main jet in place was still the ultra-lean, original 125 main jet! The most important ingredient in the uncorking process for a Honda XR650R motorcycle engine is the unrestricted rubber intake manifold and a jetting change to a 175 main jet and 68s pilot jet (base line at sea level). Exhaust modifications help further, the stock OE muffler's exit flow and end cap are ridiculously small for a 650 thumper! How important is the 175 main jet and 68s pilot? Important enough to be the OEM jet sizing on all Honda XR650R engines sold outside of North America! The U.S. engines were leaned to the limit by E.P.A. requirements, and California models (XR650R AC designation) were even more restricted by a draconian reshape and air flow restriction in the rubber intake manifold and the intake air box. So, this uncorked, non-California model had its exhaust opened and uncapped—plus the removal of air intake box restrictors. The EPA regulated (non-California) cycle already had the open, round intake manifold. It was in severe need of the 175 main jet, however, which the dealer neglected to install with the power tuning! The result is clear. Despite the low mileage, this engine was busy overheating its upper cylinder and valves. Upon tear down, which you can follow in the HD video linked above, the engine's upper cylinder looked more like a Baja 1000 Race finisher than 1000 miles of reasonable recreational riding. Fortunately, the previous owner had used quality lubricant and changed oil filters regularly. The XR650R's unique liquid cooling (the only XR to ever offer it!) also helped minimize damage and isolate the wear to the cylinder plating, piston skirts, rings and valves. The main engine assembly is still in near-new condition. I'm now in the process of rebuilding the upper engine. The head and cylinder have been sublet to L.A. Sleeve Company. My approach will likely be an alloy iron/chrome/moly, patented L.A. Sleeve liner in place of the factory Nikasil. Though many are fans of Nikasil, I'm not thrilled that's its only a "plating" thick. This Honda XR650R has a lot of work ahead, and it must be ultra reliable. I may consider a Stage 1 Hot Cams alternative, mainly to eliminate the auto-decompression mechanism on the OE camshaft. Compression ratio will remain the stock 10:1 with the new upgrade piston, enough squeeze for higher altitudes and the limit for kick starting and long piston ring life! Quality machine work, a fresh cylinder and upgrade piston choice, renewed valves and proper assembly technique will have this motorcycle living up to its legendary reputation—with a 175 main jet and 68* pilot jet in its Keihin carburetor! Follow the rebuild how-to coverage at the in 1080P HD video at the "Road Ready with Moses Ludel" YouTube channel! *Note: The carburetor now has a straight 68 jet installed, and I will see if the 68s is necessary. There is a difference in the flow between these two varieties. Honda's Power-Up Kit does call for the 68s and also a needle change if necessary. I may need to fine tune further for northern Nevada and the Sierra. Our home base is 4,100 feet elevation and high desert; the average/mean elevation at Nevada is 5,500 feet. I did drop the 175 main jet down to a 172, a slight compromise for our local altitude and runs. I can still run the bike from sea level to 7,000 feet with this main jet although from 4000-7000 feet, the carburetor and engine run progressively richer. The XR650R engine can "tolerate" this rich mix for brief runs. Ideally, I would rejet for each 1000 feet of elevation change. I use Sea Foam Motor Treatment in the fuel to keep the upper engine clean and watch both the spark plug and tailpipe coloration closely. Moses

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

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

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

Demand for more off-pavement motorcycle coverage has led to the launch of 'The Off-Road Motorcycle Channel' at the 4WD Mechanix Magazine's HD Video Network! The new channel covers dirt, off-road and dual-sport motorcycles, including tech how-to, step-by-step tuning and repairs, troubleshooting, backcountry riding and survival tips—everything related to off-road and dual purpose/dual-sport motorcycling! Inspired by the needs of the magazine's 2000 Honda XR650R motorcycle, the channel launched with HD video tech how-to coverage in Vimeo Pro 1080P full-screen detail. Whether you own an iconic XR650R Honda big-bore XR thumper motorcycle or a similar four-stroke, overhead camshaft motorcycle, you'll find the launch coverage of interest. The Honda XR650R cylinder head inspection after tear down. See the full HD video coverage. Check out 'The Off-Road Motorcycle Channel' playlist at: http://www.4wdmechanix.com/The-Off-Road-Motorcycle-Channel.html! Moses

The magazine's Honda XR650R performs remote field work as an HD video filming platform. Reliability is essential. After purchasing the bike in non-running condition, I ran a compression test when the engine refused to start. I moved from the simple compression test to a full-fledged cylinder leak down test, the pinpoint diagnostic tool of choice. Want to know more about a leak down test? Click here for the 4WD Mechanix HD Video Network feature and details on the leak down test! High cylinder leakage called for a top end inspection and repairs. That tear down for inspection can be found at the magazine as the HD video how-to: http://www.4wdmechanix.com/Honda-XR650R-Motorcycle-Upper-Engine-Rebuild-Part-1-Tear-Down-How-to.html. At left is the cylinder leak down test covered in the HD video how-to. At right is the actual top engine tear down, part of the current rebuild. See both HD videos at the magazine for details! The step-by-step teardown, rebuild and assembly are now a single HD video streaming rental at Vimeo On Demand. Included in this rental is a bonus feature on valve adjustment (which is also available as a separate streaming rental). You will find this 54-minute feature at: http://www.vimeo.com/ondemand/hondaxr650r. Here is a review of that rental video: "Coming across this video couldn't have been more fortuitous - both in timing and content. I happened to inherit a motorcycle of the exact same type and with the exact same problems as the one starring in the clip. The author/producer treats the subject thoroughly and with close-ups giving great detail of the matter at hand. Not only that, he has an online magazine with a forum through which he is eminently available for input and feedback. Having watched this gave me the confidence to embark on the solution on my own - saving loads of money and learning in the process."—David E.

Good, Bishie...The multitude of "troubled devices" that were in the DTCs cannot possibly become defective following one fuel stop. The DRB-III is great, it can actually take individual devices for a test sequence...In the long run, you'll save considerable money. The diagnostic time for a DRB-III scan is affordable by comparison and far more conclusive. Please do keep us posted...I'd like to see you able to pinpoint the issue, perform an affordable remedy, and feel confident that the WJ is reliable once more... Moses

Josh, there's a simple test for the vacuum issue. Hook up a vacuum gauge to the EGR line (a "T" if you prefer testing real time performance). Measure the available vacuum to the EGR valve with the engine idling, throttle closed. Open the throttle and watch the vacuum change. Note where the EGR valve opens in terms of engine-supplied vacuum. Keep in mind that EGR is often routed through a thermal vacuum switch to prevent EGR function when the engine is cold. You may need to perform this test with the engine cold and also warmed up. Additionally, you can hook a vacuum gauge/hand pump to the EGR valve itself. With the engine idling, apply vacuum to the EGR valve and see if you notice the same "roughness" that you've experienced when the vacuum supply line is hooked up. This will be your true test of both the EGR valve and the trouble symptom or roughness you experienced. Here are details on testing the EGR system outside of the EGR valve itself: 2.5L TBI EGR Testing.pdf Your Jeep is now far more reliable, and you're well prepared for backcountry use. It's very important with a Jeep 4x4, or any other 4x4, to have a dependable and predictable powertrain. Off-pavement, you'll need that highly stable idle, immediate response on throttle tip-in and performance on demand...You're now a troubleshooting "expert" on Jeep 2.5L TBI, which should make you popular in early Jeep 2.5L TBI circles... You did it, Josh! Moses

Josh, this is great news. You rode it out, learned a bunch and solved your Jeep's problems! Motor Man looks like quality, OE type parts. As for the EGR, check your vacuum hoses. The EGR should not open at an idle, as it uses a "ported" vacuum source. Ported, like with a carburetor, means vacuum sourced from above the throttle valve. Ported vacuum will be near zero at a closed throttle, then pick up immediately as the throttle opens, then drop to nearly nothing at wider throttle openings. The EGR actually has a positive function in addition to lowering NOx for tailpipe emissions requirements. The EGR cools the upper cylinders from as high as 4800-degrees F to below 2500-degrees F for NOx reduction. This dramatically reduces risk of detonation/ping and upper cylinder fatigue. If your EGR does not seat completely, that could be a defective or clogged valve. From what you describe, though, the EGR does work fine with vacuum removed. When your vacuum hoses are correctly hooked up, you will have close to zero vacuum applied to the EGR when the throttle is closed (idle) and ported vacuum is very low. Identify a ported vacuum source for the EGR. Congratulations, Josh! Moses

Bishie, welcome to the forums, let's see if we can help with your troubleshooting dilemma. As you likely know by now, here are the DTC definitions for your trouble codes: P0340—No camshaft signal at PCM P1765—Transmission supply relay control circuit voltage at unexpected level P1391—Intermittent loss of crankshaft or camshaft position sensor P0531—Air conditioning refrigerant pressure sensor circuit P0761—Shift solenoid stuck C214C—Emissions management issue P0301—#1 Cylinder misfire While the persisting code is a shift solenoid stuck issue, there is more to this. First of all, I'm not into the philosophy that a DTC code means an immediate call for new parts—especially when you get a constellation of codes at one time and some never come back once cleared. This "global" kind of trouble codes, when it occurs suddenly (like after filling up with fuel or any other single event), can often point to a defective PCM. While a backfire through the intake can be a camshaft position or crankshaft position sensor issue, a variety of other problems can cause a backfire. A defective or malfunctioning PCM can make the entire powertrain and chassis system seem like it's packed with defective components. I understand that you have tried to be logical with the information offered by the PCM/DTCs. Let's first take this back to the original problem and its starting point. You mention filling up with fuel to the brim. This could be an issue of bad or incorrect fuel or an emission system issue caused by over-fueling the system. It sounds like that initial trip home was in limp mode, which is often triggered by a defective O2 sensor. This is possible and could also relate to fuel quality or the type of fuel in the system. Any of these conclusions would encourage digging deeper or replacing parts. You followed the logic, or illogic, of these thrown "diagnostic codes". (If the PCM is actually defective, the codes thrown do not represent parts failures but rather the inability of the PCM to interface, read or drive these devices.) The wide array of unrelated trouble codes points to a possible universal electronic problem and not a slough of mechanical parts that suddenly and mysteriously failed. Think of the PCM like a motherboard in a PC computer. If the motherboard fails, all of the data and in-and-out information flow gets compromised. Although the PCM is supposed to interrogate itself, they often fail without a trace. If this were my Jeep, I would first unplug the PCM and check the connections for corrosion or damage, then carefully plug the connectors back into place to see if that corrects anything. If not, and if you have access to another PCM for this particular model, consider replacing the PCM or at least testing the vehicle with another PCM. In your case, there's also much to be said about scanning the system with a Chrysler dealership DRB-III scan tool for OBD-II. The cost of a diagnostic check would be far less than the expense of needlessly replacing a laundry list of parts that could be erroneously showing up on the MIL as defective, some storing codes in the PCM. The PCM could very well be defective. Caution: I did a quick look around the internet for a PCM price. They range from $450 to $600, presumably new as there was no core charge. This is quite expensive for experimenting and would likely be a part that cannot be returned unless defective. Find a much less costly solution if you can...One approach would be a recycling yard, the lowest priced used PCM you can find for your model, it can always be re-flashed, although again, that would call for the dealership DRB-III scan tool...A dealership scan is looking cheaper all the time! This is a start...Get back to us with your next step and any conclusions...Glad you joined the forums! Moses

AusJeep, you have me thinking in reverse!...I have reasoned that your RHD driver's door switching is my left (driver's) door in the U.S. model. (Please look at the PDM module that I replaced in our Jeep; see the magazine article. Does that look similar to the module you bought at the recycling yard and installed?) On the U.S. model, the PDM (passenger door module) contains the relay and master switching circuit. Is that the kind of switch you replaced at your left front door? To answer your question about the DDM, Mopar notes offer a clue. Keep in mind that they talk about the U.S. model with LHD: "The DDM also contains an integrated circuit to support the one-touch down feature of the driver side front door power window..." The driver door one-touch down switch would affect the driver's window at least. See my highlights in the Mopar comments below. The DDM could also have a defect in the power window lockout mode, in which case changing the DDM could resolve your problem. Again, if that's not your source of trouble, you are still ahead to snag that recycling yard driver's door switch. The price for a new switch can only go up over time...Generally, the driver's door switches operate more than the other switches and should wear out sooner. At my how-to article within the magazine (click here for access), I offer my comments plus more details from Mopar: My comment: The symptoms for a defective right front door lock and window switch on our 1999 Jeep XJ Cherokee were three-fold: 1) the passenger could not operate the power window or door lock, 2) the driver could not operate the passenger window or any door locks, including the rear hatch door, from the driver's door switch panel, and 3) the remote key fob door lock activator did not work. The driver could operate the other three power windows. (Switch replacement begins with the door panel removal.) Passenger side (LHD) door lock and window switch. Mopar's description...Here are the official functions of the Driver and Passenger Door Modules (switches): "A Driver Door Module (DDM) and a Passenger Door Module (PDM) are used on all models equipped with power locks and power windows. Each door module houses both the front door power lock and power window switches. In addition to the switches for its own door, the DDM houses individual switches for each passenger door power window, a power window lockout switch and the power mirror switch. The PDM contains the control circuitry and the power lock and unlock relays for the entire power lock system. "In its role as the power lock control module, the PDM receives inputs from the battery, the ignition switch, the DDM, the driver door ajar switch, the key-in ignition switch, and the headlamp switch. It also receives a hard-wired input from the remote Keyless Entry (RKE) receiver, if the vehicle is so equipped. In response to these inputs, the PDM sends the proper outputs to control the power lock motors through its integral power lock and unlock relays. "The DDM and the PDM are mounted to their respective front door trim panels. The DDM and PDM are serviced individually and cannot be repaired. If the DDM or PDM, or any of the switches and circuitry that they contain are faulty or damaged, the complete DDM or PDM unit must be replaced." Our system's symptoms met each of the requirements for a defective PDM. We ordered the right front door switch (your left front door) from a Mopar source. I replaced the one switch and solved all of our problems at the same time. Let us know if the DDM completes your repair, AusJeep. Moses

Good news! Sounds like parts that will work and replicate the OEM pieces...You now have an adjustable regulator—and the pressure tester to verify spot-on 14-15 PSI fuel regulation at the TBI unit! Did you take your tester to work and check the accuracy of the Harbor Freight fuel pressure gauge? Probably a good safeguard as you set the new regulator bowl's adjuster screw. I doubt whether they can "pre-set" these adjusters to exact pressure. Let us know how close the adjuster is "out of the box". I would guess that you'll be setting the pressure adjustment... Moses

Josh, I'm curious about Motor Man and the regulator parts, as finding these parts is unusual. Most of the 2.5L TBI pieces are not available from Mopar any longer. The cohort of Jeep engines that use Renix TBI would be 1986-90 XJ Cherokee 2.5L and '87-'90 Jeep Wrangler YJ 2.5L fours. I'm wondering what/where Motor Man pieces come from, whether they are NOS Jeep/Mopar or another source? Let us know. Below is a 1987 YJ Wrangler engine block (side view) for those unfamiliar with this engine. For detailed information on tuning and troubleshooting a 2.5L TBI four, see my 2.5L four 'how-to' article coverage at the magazine with a full set of photo illustrations: Moses

Well, the good news is that you now have an extra module, and considering the price of a RHD window module, you'll want a spare on the shelf at your garage! Here is the entire troubleshooting flow for your window problem, the official Mopar version. I even added a wiring diagram from the XJ Cherokee Manual...Note that the circuit breaker at the Power Distribution box is high on the list. Read this through, you'll know what to check next. Let us know what you find. Moses XJ Cherokee Power Window Troubleshooting.pdf