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  #16  
Old May 28th, 2019, 11:48
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XJensen XJensen is offline
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Re: Misfire cylinder 5

Update, all test have looked good... one this is the SMOG place couldn't run the test the last time I brought the jeep in. They claimed the test machine could not communicate with the jeeps computer.

I took it to a friends house to run it on his scanners and he was having trouble connecting as well. My bluetooth module does not seem to have any issues.... i still believe the misfire must be heat related. I had the exhaust manifold heat shield off when I ran over to my neighbors, injectors still wrapped, and threw a misfire on 3 & 5 when I restarted. This is what I would expect and the only lead I have to follow at this point.

I have a spare computer from my old jeep I might swap in as well. The one in there now is a re-manufactured unit.... I will look for leaks around the precats as well
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  #17  
Old May 29th, 2019, 02:08
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Re: Misfire cylinder 5

Mystery solved. #6 tube is cracked on the exhaust manifold. Hooked up the shop vac and could feel the air, sure enough about a 1.5" long crack.

It is pointed right at the #5 intake just below the injector.
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  #18  
Old June 17th, 2019, 14:09
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Re: Misfire cylinder 5

Replaced with a Banks Header, got it quick and it is CA CARB compliant. everything went great and runs awesome, or so I thought. It through a misfire on cyl 6 now and the SMOG shop claims once again that my jeeps computer will not talk to theirs.

I think it is throwing the code and the test machine is aborting the test. I am going to recheck for leaks and try it again at a new shop. The place I had been taking it to routinely leaves the jeep running before inspection, during test and during the visual with no airflow. while the jeep shouldn't misfire anyway this is not helping...
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  #19  
Old August 20th, 2019, 22:29
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Re: Misfire cylinder 5

Alright, a lot has gone one since my last post and I would like to get it out to hopefully help someone.

I feel like I have jumped down a big rabbit hole. I swapped in my old ECU and it ran like a dream, I couldn't believe how smooth it ran and it has been so long I forgot how much better it could be. I went on a 20 minute drive and then it started running like crap again. I assume it was because it was running on default settings and once the data came in from the sensors the crap data screwed with the timing.

I started getting a misfire in cyl 5&6....

I pulled the Cam Sensor and the sensor looked to be in less than ideal condition and the oil pump drive had some play in it so I replaced it. I also found some small vacuum leaks in the lines feeding from the intake manifold. intake pressure got a little better but still weak at about 15# at idle.

This is where things started to get weird, but finally started getting other codes to help me out. I got misfire codes across more cylinders and a high voltage code on bank 2 downstream O2 sensor. turns out the O2 sensor wires were rubbing the bell housing and grounding out periodically.

I replaced the sensor, I had a spare set from my old jeep. I also got a temp moving pass from the DMV and ran the Rubicon for SierraFest with the Sierra Chapter!

Driving up the hill it was getting hot when pulling hills, 145 range. the dash gauge was crap and was not far from normal but I had my OBD2 hooked up to the Torque app. When I got to the trailhead at Loon it had codes for the bank 1&2 upstream sensors and misfire codes on a couple cylinders. I replaced the bank 2 upstream sensor, forgot the other sensor at home so only got to do one.

Ran the con just fine and running rough, first time up Soup Bowl too!

by the time I finished the trail I had misfire codes only but I had codes for cylinders 3,4,5 & 6.... I figure at this point, given the behavior with the ECU and the new Cam it has to be the crank sensor.

New mopar sensor arrived today so we shall see. Any other idea in case this does not work?
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  #20  
Old September 6th, 2019, 09:51
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Re: Misfire cylinder 5

Swapped in the crank sensor. ran amazing for a few minutes then started up again. misfires on 3&5 and complaining about the TPS voltage reading. Swapped the TPS and still misfiring. This has got to be some kind of ground issue or something.....
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  #21  
Old September 6th, 2019, 12:21
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Re: Misfire cylinder 5

When my 2000 started doing the same thing, it turned out to be the wiring harness. It wasn't until I tore into the harness that you could tell what was happening. Previously during point to point testing all showed good, it was insulation breakdown that allowed shorting between the injectors. The O2 sensor wiring didn't look any better.
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  #22  
Old September 6th, 2019, 12:35
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Re: Misfire cylinder 5

that is interesting and I have thought about the harness. My shop said they can me a new recreated one for $1200. Wish I kept mine from my last part out, that jeep was in great shape.

I did open up the loom from the injectors to the PCM. everything traced to the injector and looked OK. I mean the wires by the connectors look questionable on everything...

looks like I might have to try a junk yard harness. thanks for the comment, i appreciate it more than you know.
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  #23  
Old September 6th, 2019, 12:45
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Re: Misfire cylinder 5

A little long but it details my voyage down this road. It's been great since
https://naxja.org/forum/showthread.php?t=1145993
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  #24  
Old September 11th, 2019, 11:44
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Re: Misfire cylinder 5

Looks like I might be missing the grounding strap between the firewall and the head/stud. Reading more about my issues this sounds like it might be the or part of the larger issue. Going to slap one on this weekend and will see how it goes.
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  #25  
Old September 11th, 2019, 19:45
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Re: Misfire cylinder 5

Quote:
Originally Posted by XJensen View Post
Mystery solved. #6 tube is cracked on the exhaust manifold. Hooked up the shop vac and could feel the air, sure enough about a 1.5" long crack.

It is pointed right at the #5 intake just below the injector.
Is this a bad idea, your potentially throwing debris into the engine,no?
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