I have a 2002 4.0 and I keep getting po306 cylinder 6 misfire. I've had several PCMs from wrangler fix.com they keep messing up but so far they have been good about honoring their warranties. I've changed coil pack and recently had a brand new ATK replacement engine put in. The new motor (I used all my old intake and stuff) is now giving me the same cylinder 6 misfire code. Wrangler fix is sending me another PCM next week. What can I do to eliminate this code and why to PCMs keep going bad? Also where else can I get a PCM computer besides wrangler fix. I'm in over my head with this jeep and I have way more in it than it's worth. But I love my Jeep. Please help Jeep people.
Continuous P0306 problem
- Thread starter Jellis
- Start date
You don't want to get a replacement PCM anywhere other than @Wranglerfix, trust me. Why would you?
To speak to your issue, when things like this happen and there seems to be no fix, I always suggest digging deep into the wiring harness to look for breaks in the wiring. Sometimes you have to take the entire wiring harness apart to look.
It's the last place anyone thinks to look.
To speak to your issue, when things like this happen and there seems to be no fix, I always suggest digging deep into the wiring harness to look for breaks in the wiring. Sometimes you have to take the entire wiring harness apart to look.
It's the last place anyone thinks to look.
There is a wiring harness that is routed along the firewall from the PCM which is routed behind the valve cover and around the threaded head stud in the right rear corner of the head.
Thoroughly inspect the split wire loom and harness wiring in the proximity of the threaded head stud.
This threaded head stud is known to wear thru the plastic split wire loom and wiring harness plastic insulation exposing the copper wiring. This will cause intermittent and continual problems depending upon the severity of the damage to the wiring harness.
I placed a spare rubber spark plug boot over the threaded head stud to ensure I do not have this problem.
Thoroughly inspect the split wire loom and harness wiring in the proximity of the threaded head stud.
This threaded head stud is known to wear thru the plastic split wire loom and wiring harness plastic insulation exposing the copper wiring. This will cause intermittent and continual problems depending upon the severity of the damage to the wiring harness.
I placed a spare rubber spark plug boot over the threaded head stud to ensure I do not have this problem.
Yes the miss is the only symptom. Other than so low engine rattling at take off. Not sure what that it. I assumed with the new crate engine it is just being broken in. I will check the wiring harness thanks for the info.
Faulty spark plugs or wires
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector(s)
Burned exhaust valve
Faulty catalytic converter(s) Stuck/blocked/leaking EGR valve / passages Faulty camshaft position sensor
Defective computer.
Here is a list of things to check. I can test the ecm if you’d like to send it into us.
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector(s)
Burned exhaust valve
Faulty catalytic converter(s) Stuck/blocked/leaking EGR valve / passages Faulty camshaft position sensor
Defective computer.
Here is a list of things to check. I can test the ecm if you’d like to send it into us.
For future readers, your PCM fixed my P0300 codes that I thought were heat-soak related. Super appreciative of that.
But, if OP keeps getting the same code with different PCMs then he probably wants to look at wiring. AndyG just fixed a similar code by cleaning up the pins at the PCM connector.
The folks who have been giving advice know what they are talking about.
Literally checked and or changed all of that and I'm on my 3rd ECM from you guys. Mark is sending me another 1 this week. Also when I clear the code it doesn't come back all the time but I can hear it misfiring. The same as if the light was on so the problem persists with or without light which make me thing It's the computer again. Thanks for always honoring the warranty wrangler fix. I do appreciate that
He's not wrong...there are many things that can cause a misfire (issues related to compression, fuel, spark).
Looks like he's trying to help. Take a look at the female pins on your PCM connectors. Andy just fixed a misfire code by cleaning pins up...also look to see if they are pushed.
Looks like he's trying to help. Take a look at the female pins on your PCM connectors. Andy just fixed a misfire code by cleaning pins up...also look to see if they are pushed.
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You did a compression or leak-down test? If not you can rent a compression test for a local auto parts store.
doesn't matter ! new things can be bad, they can also be messed up on installation, like I said it's easy enough to swap 2 plugs and eliminate that as a problem.
Old Russian proverb made famous by Regan.
On that same note I'd be doing the compression and leakdown test. Best case scenario you have benchmark numbers for 250k miles from now when you have your next issue.
Worst case you find your solution to your 306 code.
Two people posting in the last couple of days about their brand new engines being shit.
-Mac
I learned that lesson when fixing F-14 Tomcats.
Yea, I'd at least check compression. You might have a new engine that needs fixed.
This. We hope it's not your engine, but don't be afraid or too proud to check. Your goal is to locate and fix the issue, not have it be what you want it to be.