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Discussion Starter · #1 ·
I have a 2012 wrangler that keeps throwing a cylinder 4 misfire after replacing the following: cylinder head replacement, intake, new spark plugs and coil packs. It’s also had a recent software update. It has 92,000 miles on it. At this point what’s left? The dealer can’t figure it out and sometimes the check engine light goes off and on by itself.
 

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I just went through the same thing on my16 jku sahara for cylinder 2.

Was put of town when the CE light started blinking and beeping. Brought it to the local dealership who diagnosed it as a bad head. Had the head replaces. 15 miles from dealership on way back to my home the light came back on.

After 300 mile drive brought to my local dealer and was diagnosed with cylinder 6 misfire. They replaced the head under warranty. Again 15 miles after picking it up the CE started blinking and beeping.

Brought back to local dealer only to find it's now cylinder 1.

Long story short after them having the jeep for a week they found a TSB with this issue and all they needed to do was updated one of the computers.

Left me questioning whether I needed the new head in the first place. I have confidence with my local dealer but the first one that changes the head not so much, requested to see the old parts but they were "not available" when I showed up.

Have them check for computer updates updates and hopefully that will cure your misfires
 
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There are only 2 things left, the PCM and the wiring from the PCM to the coil pack. When it throws a check engine light, what codes are you getting?

In my 12 , I had a Cyl #2 misfire. Symptoms were that it wasn't always present but it presented itself, I would get the MIL lamp that would eventually clear itself only to return once the engine was under a load. My solution to the issue was 2 fold. 1st was that I had a bad PCM (driver fired the coil all the time) which caused the #2 coil to go bad and 2nd was the wire from the PCM to the #2 coil went open when the engine was hot.

You might want to sent out the PCM to someone to have it tested. I used Auto Computer Performance in Margate FL who tested mine, found the driver actually damaged the board and sold me a replacement computer cloned from my computers programming. Once I installed that, I was able to troubleshoot the trigger wiring. DO NOT use Flagship 1 or any of their associated companies for a computer diagnosis or exchange. I attached the 12 3.6L engine wiring diagram for you (which was super hard to find)
 

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Discussion Starter · #4 ·
There are only 2 things left, the PCM and the wiring from the PCM to the coil pack. When it throws a check engine light, what codes are you getting?

In my 12 , I had a Cyl #2 misfire. Symptoms were that it wasn't always present but it presented itself, I would get the MIL lamp that would eventually clear itself only to return once the engine was under a load. My solution to the issue was 2 fold. 1st was that I had a bad PCM (driver fired the coil all the time) which caused the #2 coil to go bad and 2nd was the wire from the PCM to the #2 coil went open when the engine was hot.

You might want to sent out the PCM to someone to have it tested. I used Auto Computer Performance in Margate FL who tested mine, found the driver actually damaged the board and sold me a replacement computer cloned from my computers programming. Once I installed that, I was able to troubleshoot the trigger wiring. DO NOT use Flagship 1 or any of their associated companies for a computer diagnosis or exchange. I attached the 12 3.6L engine wiring diagram for you (which was super hard to find)
Thank you! It’s cylinder 4. I will def check this out.
 

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I have a 2012 wrangler that keeps throwing a cylinder 4 misfire after replacing the following: cylinder head replacement, intake, new spark plugs and coil packs. It’s also had a recent software update. It has 92,000 miles on it. At this point what’s left? The dealer can’t figure it out and sometimes the check engine light goes off and on by itself.
I have a 2013 JK. Recently had misfire on 2, 4, and 6. They replaced all my rocker arms.
 
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