JamesHigdon Posted November 3, 2012 Report Share Posted November 3, 2012 I hate dealing with these trucks, it always seems to be some off the wall problem. The truck came in with a solid misfire and no codes which I seem to have tracked to cylinder 6. The injector wiring had been messed with and taped up but all of the injectors pulsed fine. I ran a spare coil (it has a large single coil) on it and checked the original, the spark doesn't seem to be the issue. I switched injectors front to back and the miss didn't follow the injector. I can confirm it is cylinder 6 because I get no pulse change when pulling that injector wire off. I ran the compression and it's 120+psi on that cylinder. What could be up here, good compression rules out most mechanical problems and the valve issues these trucks are known to have and it doesn't have spark plug wires to mess up so I'm truly stumped? Editing to add a few things, first its an 01 Jeep Grand Cherokee with the 4.0l I-6, 2wd with the X code engine. I only bumped until I saw compression on cylinder 6 the first time, went back and re-tested to full compression with 152 on cylinder 6 and 150 on cylinder 1. I changed the spark plugs 1 to 6 just now and the miss didn't follow the plug so thats not it. To re-cap, swapped the injectors and it didn't follow the injector, same with plugs, good injector pulse to cylinder 6, good spark at cylinder 6 and no oil on the plug. The only thing at all that I've noticed so far is the plug I pulled to swap with 6 (number 1) had some signs of being lean and/or very slight oiling. Link to comment Share on other sites More sharing options...
HiTech Posted November 4, 2012 Report Share Posted November 4, 2012 I DRIVE A 01 ,AND HAD THE CHECK VALVE ON THE BRAKE BOOSTER GO BAD ..BUT IT WAS NUMBER FIVE IT MESSED WITH ....SPRAY SOME STARTING FLUID AROUND THE INTAKE . I HAVE HEARD FROM OTHERS THEY HAVE HAD TO REPLACE THE INTAKE GASKET ... Link to comment Share on other sites More sharing options...
JamesHigdon Posted November 4, 2012 Author Report Share Posted November 4, 2012 I will check the valve, a vac leak does make a ton of sense though, I will check that out tomorrow, thanks. Link to comment Share on other sites More sharing options...
HiTech Posted November 5, 2012 Report Share Posted November 5, 2012 read up they have had problems with ecm programing ....common problem it seems . Link to comment Share on other sites More sharing options...
JamesHigdon Posted November 6, 2012 Author Report Share Posted November 6, 2012 Yea, unfortunately we are VERY familiar with Chrysler and their inability to properly program any software from the factory. The issue does appear to be an intake manifold vacuum leak but here's the kicker...its on the other end of the motor! Link to comment Share on other sites More sharing options...
HiTech Posted November 6, 2012 Report Share Posted November 6, 2012 Yea, unfortunately we are VERY familiar with Chrysler and their inability to properly program any software from the factory. The issue does appear to be an intake manifold vacuum leak but here's the kicker...its on the other end of the motor! reminds me of a leaky roof ...starts at one end of the house only to travel across the house before it comes through the light fixture ... Link to comment Share on other sites More sharing options...
JamesHigdon Posted November 9, 2012 Author Report Share Posted November 9, 2012 Ok, fixing the intake gasket leak seems to have made the motor run a little better but not right. We have also replaced the cam-shaft synchronizer because it was notchy when spun. We went back and ran compression all the way across the motor and came up within + or - 5 psi of 150 psi. I am pretty much stumped. I also went back with the osciliscope and checked the pulsing on a few of the injectors and the pulses on 6 matched the others so I'm leaning away from a ECU issue? Anyone? Link to comment Share on other sites More sharing options...
HiTech Posted November 9, 2012 Report Share Posted November 9, 2012 well heck ......out of the box . but i remember having an issue with number three on a 93 dodge van .misfire and found the intake spring was bad compression was fine on all ...never hurt to take a look .. Link to comment Share on other sites More sharing options...
jwmbishop Posted November 9, 2012 Report Share Posted November 9, 2012 same could happen with an exhaust spring... Link to comment Share on other sites More sharing options...
JamesHigdon Posted November 9, 2012 Author Report Share Posted November 9, 2012 Well...it just gets deeper. We pulled the plugs this morning to make sure the cam synchronizer was set on TDC, which it is. We put a fresh set of champion OEM plugs in it because the old plugs while newish looking where fouled. I double checked the connector on that injector and made sure the prongs where contacting the injector. The longer I look at this truck the more I think someone has been chasing this issue for a long time. The truck had, when we bought it a rebuilt ECU, a new cam synchronizer (that was already notchy), newer champion plugs (which where already fouled), the valve cover has been off recently, the oil pan has been off recently and all the wiring has been sorted through with a few of the injector connectors replaced. Edit: We pulled the valvecover and checked the valve-springs to make sure all that was square, couldn't see any issues. We went so far to run the engine with the cover off to confirm nothing was out of line and all was working correctly. Edit2: Fuel Injectors are all new The only lead I have right now is that while running the fuel pressure is high-out of range. The factory spec is 49.2 +/- 5 psi and we are running at about 65 psi. I am beginning to wonder if maybe 10 psi is enough to cause plug fouling? I have never had fuel pressure out of range by that small an amount (high or low) cause major issues like this? Link to comment Share on other sites More sharing options...
4cylfordz Posted November 9, 2012 Report Share Posted November 9, 2012 o ten psi can do all sorts of things check the fuel pressure regulator for blockage. typically when one fails they won't keep enough pressure. so I would check for trash in the return to tank system. Link to comment Share on other sites More sharing options...
HiTech Posted November 10, 2012 Report Share Posted November 10, 2012 this starting to look like that darn yukon i had hell with ..finally got lucky ...... Link to comment Share on other sites More sharing options...
JamesHigdon Posted November 11, 2012 Author Report Share Posted November 11, 2012 Well...after working through everything else I noticed the plugs where fuel fouling pretty often so we pulled out one of the pre-cat O2 sensors and the idle smoothed out some, I pulled out another and the idle smoothed out more and we started getting a response from the #6 cylinder. The truck has a split manifold (123/456) and it seems both of the pre-cats are clogged as well as the post cat. The truck has a rebuilt motor; I am leaning towards the previous motor grenaded and fouled the cats, they rebuilt the motor which then misfired so they then replaced every part on the motor trying to chase the misfire. We are going to replace all the cats and go from there! Link to comment Share on other sites More sharing options...
JamesHigdon Posted November 14, 2012 Author Report Share Posted November 14, 2012 The only thing more frustrating then changing a part and not having it make any difference is changing a part and having it make a difference and not fix the problem. We replaced the head pipe with both pre-cats and while it seems to have helped the truck run smoother I am still not getting any change when I pull the #6 injector wire and the truck just runs rough in general. To add a little to the puzzle the #6 plug looks great now, it looks like it's firing well, has heat signatures and no fouling. To add a little more when we where cranking the motor with the coil totally pulled off the engine we kept on sputtering and backfiring like it was getting spark?...now I'm really confused. Link to comment Share on other sites More sharing options...
HiTech Posted November 14, 2012 Report Share Posted November 14, 2012 i am going to talk to my buddy at dodge .i worked with him 20 years ago at dodge .one of the best who knows a ton .most likely he has seen this ...i Link to comment Share on other sites More sharing options...
4cylfordz Posted November 14, 2012 Report Share Posted November 14, 2012 I dont know if you can but can you swap the coil rails and see if the miss moves? Link to comment Share on other sites More sharing options...
JamesHigdon Posted November 18, 2012 Author Report Share Posted November 18, 2012 Well, I folded and took it to the dealer. They pinpointed degradation in the injector driver for the #6 cylinder, when I told them we checked that cylinder with an oscilloscope he asked what that was...so they are putting a computer in it to see what happens. We will see. Link to comment Share on other sites More sharing options...
jwmbishop Posted November 18, 2012 Report Share Posted November 18, 2012 when I told them we checked that cylinder with an oscilloscope he asked what that was... Thats just too funny. Makes me feel like a REAL old fart as osci's were top of the line tech when I got my first NIASE cert in tune up. circa 1977 Link to comment Share on other sites More sharing options...
JamesHigdon Posted November 26, 2012 Author Report Share Posted November 26, 2012 It wasn't the ECU...the dealer STILL has the truck. Link to comment Share on other sites More sharing options...
HiTech Posted November 26, 2012 Report Share Posted November 26, 2012 could be the wiring harness ......also where the harness connects at the cab.....when i worked at dodge we had tons of problems with the pin connections at the ecu and sometimes going into the cab .. Link to comment Share on other sites More sharing options...
JamesHigdon Posted December 4, 2012 Author Report Share Posted December 4, 2012 Its back over here now after a prolonged stay at a local CJD dealer to remain nameless...They installed an ECU that didn't really fix anything and then stuck us with a $710 tab for it so we are pretty much where we started. We have another battery of leak-down and compression tests to confirm everything is good, rechecked the fuel and spark situation and are now focusing on the ignition system. We are getting good spark to #6 but are working on a test to confirm it is at the right time which is complicated on this model by a single piece coil pack which stretches across the entire engine. The coil pack is a batch-fire affair and right now we are parring cylinders and analyzing the time difference between fuel injector fire and coil fire...our main reason to go down this path is now whenever pulled the number 6 plug is wet-fouled with fuel. Ill keep this up to date as we search through this mess. Link to comment Share on other sites More sharing options...
KISS_Racing Posted December 4, 2012 Report Share Posted December 4, 2012 Its back over here now after a prolonged stay at a local CJD dealer to remain nameless...They installed an ECU that didn't really fix anything and then stuck us with a $710 tab for it so we are pretty much where we started. We have another battery of leak-down and compression tests to confirm everything is good, rechecked the fuel and spark situation and are now focusing on the ignition system. We are getting good spark to #6 but are working on a test to confirm it is at the right time which is complicated on this model by a single piece coil pack which stretches across the entire engine. The coil pack is a batch-fire affair and right now we are parring cylinders and analyzing the time difference between fuel injector fire and coil fire...our main reason to go down this path is now whenever pulled the number 6 plug is wet-fouled with fuel. Ill keep this up to date as we search through this mess. Question... I thought I remembered You'll are EFI Live Dealers. From what my buddy was telling me and this is on the Diesel side so I know (ZERO) of what EFI has done on the gas side. That being said have You plugged in anything in to see what the ECU is doing(I'd be curious as to what is going on with fueling)? I have a feeling I know the CJD You went to and I don't care for them either. My 2004 Dodge 2500 Hemi was there and I ended up with the kitchen sink thrown on my bedcover. When I asked for a rope to tie it down they told me it was on me! (obviously kidding about kitchen sink) I have never been impressed with their techs and the fact they charged You for an ECU that didn't fix it proves my feelings towards them. Link to comment Share on other sites More sharing options...
JamesHigdon Posted December 4, 2012 Author Report Share Posted December 4, 2012 Question... I thought I remembered You'll are EFI Live Dealers. From what my buddy was telling me and this is on the Diesel side so I know (ZERO) of what EFI has done on the gas side. That being said have You plugged in anything in to see what the ECU is doing(I'd be curious as to what is going on with fueling)? I have a feeling I know the CJD You went to and I don't care for them either. My 2004 Dodge 2500 Hemi was there and I ended up with the kitchen sink thrown on my bedcover. When I asked for a rope to tie it down they told me it was on me! (obviously kidding about kitchen sink) I have never been impressed with their techs and the fact they charged You for an ECU that didn't fix it proves my feelings towards them. I've worked with EFI live but am not a dealer for their system, we've used mostly GM based systems so far. We have run a couple of different scanners on the truck and with our PCM and the new dealer PCM we have seen no misfire counters on any scanners which is curious. In relation to fueling we watched the signal to the injectors with an oscilloscope and there is zero difference in wave form, period or anything of the like. We haven't seen any real anomalies in the PCM save for it being harder then usual to access many of the sub-menu readings. This morning we went sorting through power train control wiring and found a few rough grounds which we fixed to no change. We checked fuel pressure again (57 PSI on a 49.2 +/- 5 PSI recommended reading) and checked fuel volume which was well over the 1/4 liter per 7 seconds recommendation...I am getting ready to pull the injectors and watch the fuel streams to see if it's possible we are just getting too much fuel. The fuel system on these trucks is a little odd. The fuel comes out of the pump and goes straight into a regulator/filter assembly with a return line on it, beyond that a single line feeds the rail between the 1 and 2 injectors with 6 basically being the farthest point from the regulator. I dropped out before fluid dynamics but got a lot of practical application experience in FSAE, am I right in thinking that in a dead-head system with over-capacity pressure/volume the pressure/volume will build up at the farthest point from the inlet? We have seen fuel fouling on number 6 on occasion... My lead tech just walked in with two spark plugs in his hand and asked me to tell him what I though without telling me which was which. Besides the dealer putting one oddball NGK in on #6 the much newer #6 plug had shading to the porcelain which the other plug did not. I also saw a much more pronounced heat-pattern on the older plug's ground strap, on the #6 plug it stopped about 2 tenths away from the threads. We checked the coil and saw roughly 25 KV on #6 and between 28 and 32 KV on the other plugs which is again curious but not really indicative of a problem. We are putting two new plugs in, one on #2 and one on #6 to check and see if the heat pattern changes occur again. We have also discovered today while messing with calibrations in the ECU that if we open up the IAC motor to let more air in and bring the RPM up to around 1K the misfire seems to go away (which is didn't before) and the truck has no misfire at speed (which it did before). Something has changed but what I don't know, now the misfire is only present (or maybe only noticeable) at below 1K rpm. Link to comment Share on other sites More sharing options...
4cylfordz Posted December 4, 2012 Report Share Posted December 4, 2012 Does that thing have a dist style pickup ( little sensor that bolts into where the dist would go?) or does it rely off of the flex plate to determine firing times? If it is the flying magnet type I have seen chryslers run funny when the motor has been pulled and the sensor in the bell housing not being installed properly. They have a real good tendency to be pinched back there as well. Also does it miss more when it hot? Link to comment Share on other sites More sharing options...
HiTech Posted December 4, 2012 Report Share Posted December 4, 2012 i have owned my 01 jeep 4.0 for five years .and it has always had a tiny little misfire feeling under 1k ..always seems like the iac is out of wack ..have at times idle problems but goes away in a day or two ..i gave up trying to fix that problem ......i have noticed other 01 and up 4.0 having the same problems and everyone like me gave up after spending time and money .....other than the idle problem and the misfire feeling ..they all run great ..yeah may not ever solve the problem . Link to comment Share on other sites More sharing options...
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