Have Jeep Questions? Ask a Jeep Repair Expert for Answers
Hello, my name is***** the check engine light on? Does it idle good? Thanks.
Does the check engine light flash? Do you know what codes your getting? Thanks.
P0306 is cylinder 6 misfire so this would be a problem that effects specific cylinder, most likely injector. Swap injector with another cylinder to see if misfire follows injector, if so replace. Here are replacement instructions, let me know how it goes or if you run into more questions. Thanks.
Sounds good, keep me updated. Thanks.
Use a spark tester to test spark strength on each coil lead. They should all jump a 25kv gap. Let me know, thanks.
Sounds good, let me know. Thanks.
Replace the ignition coil assembly. Let me know how it goes, thanks.
Sounds good, thanks.
Still not getting spark out of 6 or 4?
Check to see if cylinder 6 has good spark, if so next step is a compression test. Let me know, thanks.
I'm not sure what to think of this one considering you keep getting a cylinder 6 misfire with everything checking out. I'll open question back up to see if someone else has some ideas.
I don't know if this would help you, but I've seen O2 sensor wires cause similar problems, and noticing you mentioned code P0136 popping up, I think you should check the wiring from the downstream sensor all the way up to the engine harness - pay close atention at the point where the harness breaks out to the injectors.
Please let me know if that helps.
Oh. boy... I hate that cold stuff ;-( - that's why I retired to the Caribbean :-)
Take your time and let me know what you find.
Oh, well... it was worth trying - I just doesn't explain why that P0136 popped up.
Anyways, back to the misfire on cylinder 6; if we have spark and fuel and static compression is within specs, the only other thing that could cause a misfire would be valves not opening and closing as they're supposed to - I've seen sludged-up engines where a lifter fails on deceleration and the valve doesn't open properly, or holds it open so the spring can't close it.
So, we are at the point where I recommend a good engine oil flush before taking anything apart. What do you say?
OK. Make sure there are no signs of heavy sludge before doing the flush. If there are such signs, it might be too late to save that engine.
Thank you for that last bit of information. It all now starts to make sense along with that P0136 that popped up once. Go under the vehicle and start tracing the O2 sensors wiring all the way to the PCM. Check for any traces of burning by contact with the exhaust pipes or any thing that may have caused a short. If the wiring is good, then check the connectors at the PCM. If those are good, then the problem is in the PCM itself.
The reason I'm suspecting the PCM to be the cause of the issue is because of what you said about having to take the code off to make it run good. If the problem was actually caused by a misfire, erasing the code wouldn't have any effect on how the engine ran.