Need advice for misfire issue


Haaris Khan

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Been having the most annoying jeep issue in my entire life. Chasing the culprit for a misfire for a few months now as some of you might already know. I am beginning to question my own knowledge on if it is even a misfire though. I am not getting any misfire codes at all, but my jeep will sometimes run like shit and loses power. At one point my CEL was flashing but it just stopped on its own. I am getting codes P0351 - 353. (intermittent circuit interruption to the coil rail, not reaching maximum dwell time.) I am not getting any other codes at all. I was under the impression that this could be caused by three things. 1.) A bad PCM. 2.) Bad Coil rail. 3.) Faulty wiring. I have sent my PCM to Mark at Wranglerfix and it showed no irregularities. I bought a new Coil Pack (Mopar) a couple months ago but the issue still remained. I bought it out of a part out of a TJ with 66k miles, but there is still a chance it could have been faulty. So my question is now, should I continue to troubleshoot with the remaining possible culprits, or take the L and tow my jeep 3 and a half hours to the nearest jeep shop I could find. At this point I just want to be able to DD my jeep again at all costs.
 
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Jerry Bransford

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I'd suspect one of three things, in no particular order. A bad crankshaft position sensor, a bad O2 sensor, or single-tipped platinum plugs like the Autolite AP-985 or Champion 3034 spark plugs were installed.
 
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Haaris Khan

Haaris Khan

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I'd suspect one of three things, in no particular order. A bad crankshaft position sensor, a bad O2 sensor, or single-tipped platinum plugs like the Autolite AP-985 or Champion 3034 spark plugs were installed.
Replaced the Crankshaft position sensor (MOPAR), and replaced the spark plugs with NGK ZFR5N. I understand how a bad O2 sensor could make my jeep run rough or lose power, but that wouldn't be related to my codes would it?
 
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Jerry Bransford

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Closely examine the large wiring harness that passes/turns around the tall vertical threaded stud at the rear of the head. The threads on that stud are known to wear through the insulation and cause intermittent problems like you're having. Some of the wiring in that harness connects to the fuel injectors.
 
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williambmac

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I recommend doing what @Jerry said. Those codes are primary coil circuits codes. If you installed a new coil and you had your pcm tested by @Wranglerfix. then the only thing really left is a wiring issue.
I would inspect the connector @ the coil, verify there is no corrosion/water intrusion. I would then pin drag the terminals to verify proper terminal tension. A loose terminal can cause issues.
If all that is ok, then I would be inspecting the wiring harness from the coil connector back to the pcm.
There is also the possiblilty that there is an issue in the ASD circuit. I would go to the resource center on the forum and look at the wiring schematic for the ignition coil circuits. I would also be checking resistance from end to end in these circuits.
 
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Jerry Bransford

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Wrangler wiring issues are enough to drive anyone crazy. That is why (insert pregnant pause) I am going to start rebuilding harnesses!

More info coming very soon. 😎
You're just going to put the makers of crimp butt-splices and electrical tape out of business if you go and do a thing like that. :ROFLMAO:
 
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Haaris Khan

Haaris Khan

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Closely examine the large wiring harness that passes/turns around the tall vertical threaded stud at the rear of the head. The threads on that stud are known to wear through the insulation and cause intermittent problems like you're having. Some of the wiring in that harness connects to the fuel injectors.
BFF29F81-0218-4BFF-8F1F-EA0A7F78F2E5.jpeg

I can’t seem to find the stud that you’re talking about. There is a stud at the far back right of the head but it’s definitely not making contact with the wire loom in my engine. Am i looking in the right place?
 
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Haaris Khan

Haaris Khan

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I recommend doing what @Jerry said. Those codes are primary coil circuits codes. If you installed a new coil and you had your pcm tested by @Wranglerfix. then the only thing really left is a wiring issue.
I would inspect the connector @ the coil, verify there is no corrosion/water intrusion. I would then pin drag the terminals to verify proper terminal tension. A loose terminal can cause issues.
If all that is ok, then I would be inspecting the wiring harness from the coil connector back to the pcm.
There is also the possiblilty that there is an issue in the ASD circuit. I would go to the resourse center on the forum and look at the wireing schematic for the ignition coil circuits. I would also be checking resistance from end to end in these circuits.
CB1271B3-201B-4AE8-910C-EF6459B7AD27.jpeg

This is what my connector looks like. I’m not sure if it appears to be normal or not. I just pulled the coil rail and tested it with a multimeter but I am not sure if i tested it the right way. I set the multimeter to 2000k in the ohm setting and probed the boots in the order they fire (1,6, 2,5, 3,4) and each time I got a reading of 0 16. I think I somewhere that the number should be between .16 and .19. Is there a way to test the prongs in the connector attached to the coil rail with a multi meter?
 
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Haaris Khan

Haaris Khan

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View attachment 282857
This is what my connector looks like. I’m not sure if it appears to be normal or not. I just pulled the coil rail and tested it with a multimeter but I am not sure if i tested it the right way. I set the multimeter to 2000k in the ohm setting and probed the boots in the order they fire (1,6, 2,5, 3,4) and each time I got a reading of 0 16. I think I read somewhere that the number should be between .16 and .19. Is there a way to test the prongs in the connector attached to the coil rail with a multi meter?
 
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Haaris Khan

Haaris Khan

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It's there, past what you can see in your photo just past the valve cover. I have an '04 too and it's there.
Stuck my hand behind there and sure enough I felt another stud. I couldn’t feel any of the wire loom around it though, so I’m not sure if it’s rubbing against my wires and causing a short.
 
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Haaris Khan

Haaris Khan

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Just read the service manual and couldn't find anything about testing the wiring connector. It appears to look fine though I want to test the resistance of both connectors. Not sure where I should go from here.
 

Jerry Bransford

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Stuck my hand behind there and sure enough I felt another stud. I couldn’t feel any of the wire loom around it though, so I’m not sure if it’s rubbing against my wires and causing a short.
You need to get in there and look more closely. I'm not guaranteeing the wiring back there is chafed/damaged but it happens enough that I'd crawl up in there with a good light and dig back behind that lower wiring harness that is just above the valve cover. The damage that can be caused by the threaded stud can be substantial.
 
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Rooscooter

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Wrangler wiring issues are enough to drive anyone crazy. That is why (insert pregnant pause) I am going to start rebuilding harnesses!

More info coming very soon. 😎
Oh man.... I wish you'd do it for CJ's... I just put one together for a CJ 7 with a swapped early 70's 401. It's good to go now but it was a process..... a long ..... long process.

I've done some small wiring in the past but never tried a full harness until this. If my TJ starts having wiring issues I'd buy one rather than do that again.... and comparatively the CJ was, in theory, much easier.
 
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Wranglerfix

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I found a fellow that has a lot of patience and experience in harness repair. He is gathering his supply list and has an 05 LJ automatic rubicon engine harness to start with.

I will share pictures and videos of the process from beginning to end!!

Make it a great day and watch out for the crazies!

Mark
 

Jerry Bransford

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Oh man.... I wish you'd do it for CJ's... I just put one together for a CJ 7 with a swapped early 70's 401. It's good to go now but it was a process..... a long ..... long process.

I've done some small wiring in the past but never tried a full harness until this. If my TJ starts having wiring issues I'd buy one rather than do that again.... and comparatively the CJ was, in theory, much easier.
There are two good quality providers of complete wiring harness kits for CJs, Painless and Centech. I completely rewired a friend's '73 CJ with a Centech wiring kit and it was an awesome product. Each wire in the harnesses was even labeled individually for what it did.
 
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