Jk 3.6L blowing coil packs - need help

cranbiz

cranbiz

Well-Known Member
Joined
Nov 11, 2015
Location
Wentworth, NC
So at the meet and greet, I had a P0302 Cyl2 misfire and a P2305 cy2 2 secondary coil insufficient ionization. Rented a uhaul trailer and got it home. Found the #2 cyl coil pack bad with the internals coming up thru the epoxy. Changed it out and all seemed OK. Took it to Windrock Thursday and about 25 miles in, started again with the cyl 2 misfire. Ran fine at hiway speeds so I got to Windrock, pulled it apart and found the same mess with the #2 coil. Replaced it and the plug, and went wheeling Top of the mountain, same thing. Had other issues that may or may not happened due to this but anyways, I need ideas.

So, what could this be? I have been told that it could be the PCM. I have seen other people saying that they have had PCM issues cause similar issues with other cylinders. I have seen people say bad connections, say plugs, etc. @amcjeepman texted a friend Thursday night who said start with the plugs, but he had seen a similar problem on the hemi which was a bad PCM, causing the coil to fire constantly, overheating the coil. I'm leaning to getting a PCM due to my respect for James and his advice but just wanted to ask here to see if anyone else has seen this and can advise me if the PCM is the right way to go.
 
I think my bil has the same issues. I’ve reached out to me and will let you know. I think he ended up doing a comp/coils/plugs
 
His was cyl 6, but same deal... replaced coils with cheap on hand parts store coils. Later found out most are just rebuilt and still shitty. His kept overheating and back fed to pcm. His has a ripp sc so we went with ripp coils that are rated higher. He hasn’t had issue since replacing
 
The first replacement was a Mopar oem, the second was a dualast and that one I just pulled and it failed slightly differently, melted the epoxy but same result, fried coil pack. Going back out on a few to check the wiring for shorts.
 
I guess I should have posted some updates here. Sent the PCM to Auto Computer Performance in FL (NOT FS1). They did diags on it and the coil circuit was fried and the driver chip and the underlying PC Board were burned and charred and therefore was unreliably repairable (not that they wouldn't try but they wouldn't guarantee the repairs).

Got the replacement within a week and it had been cloned from my old PCM's programming which meant that my Superchips was not locked out of it. The new PCM took care of the misfires and the killing of the coil pack but I still had a P2305 error once the Jeep warmed up.

Further digging into the error found that the trigger wire from the PCM was showing an elevated resistance vs the other trigger wires. When cold, the #2 coil trigger wire was at 6 ohms cold, the other coil triggers were 0.7 ohms. Going further, the short, somewhat inexpensive and easily changed harness showed equal resistance in all trigger wires and the ungodly expensive, PITA to change harness was still showing differences from #4 and $6 vs #2.

Last night I made the decision to hack the harness and splice in an equal length of 16 GA THHN wire from the PCM connector to the coil connector. The reason for the same length was to get the wire resistance close to the same. After the repair, the wires all ohmed out at 0.7 ohms. Put it all back together and took it out for an extended test ride around Rockingham County. I tried to duplicate conditions that I knew caused it to act up and certainly got it hot enough to act up. So far, so good. It performed flawlessly.

Looks like I had 2 separate but related problems.

My best guess is I had a break in the main harness for the #2 coil wire that has some continuity when cold and went mostly open when hot as one problem and the other problem was the driver circuit in the PCM was constantly firing the #2 coil which caused the coils to fail due to overheating.
 
nerd time. because i have to.
Get some thwn-2 and replace the thhn with it.
the W gets you wet locaton and the 2 gets you oil/gas resistance and rock out with your...errr...jeep out
 
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