Well, I seafoamed it, and that seemed to help. The engine is running strong, but today when I was accellerating hard(always when RPMs past 4,000) the light starts to blink again. Then it came on steady again(blinked first for a few seconds). I haven't had the code checked yet, but I will tomorrow. I'll see if it is the misfire. If I am not hard on the accelerator, it doesn't seem to ever trigger the check engine light, so I'm unsure of what is going on at this point. If anyone has any ideas, please let me know. I'll keep everyone updated.

 

The reason i asked is that i am dealing with a cylinder one misfire. Can't seem to track it down.

 

Hey Warthog,
Definitely try the seafoam. It really improved things and the occurance of the light. I'm getting the code read this morning so I'll let you know if it is still the cylinder 6 code.

 

It was the p0306 code again, but I reset it, and drive it a little less hard and it doesn't trigger. My mechanic thinks its a Chrysler TSB, and it probably needs some sort of PCM reflash, once all the things in the TSB(which mine have) been done/fixed. I'm not too worried about it because the engine is not misfiring. It feels strong and is running fine.

 

The check engine light still periodically blinks, and if I am really hard on it, goes on steady until I reset it. It is not misfiring though, so I hope I'm not missing anything. Any recommendations as to what I should do from here on out?

 

How does that spark plug look? is there any signs of detonation or preignition?

Just an off the wall question.... how come you are pushing your jeep so hard like that?

 

IMO....with the fast blinking CHK ENGN.....you've got CAT scratch fever! the cat is getting ready to go....causing excessive back pressure...causing the carbon deposits....causing the sticky valves....get a back pressure test done at the o2 sensors to check out the cat...good luck, man.

 

I wouldn't say I'm hard on it. Every once in a while I give it full throttle up to about 60 or so, but I'm not constantly on the pedal or anything. Lately it only triggers the light, or misfire code when I exceed 4k rpm. Spark plugs were replaced.

 

If there was a crack in my exhaust manifold, could that cause the cylinder misfire? Anyone?

 

Well I had a banks torque tube header installed today. My mechanic couldn't get two of the 02 sensors off the old header. They were hard on there, so I replaced those two O2 Sensors, and also noticed a crack in my exhaust right after the flange but before the CAT. It got bigger as they worked, so I need to have it welded shut tomorrow. It's really loud now of course.

The good news is no more cylinder 6 misfire or even a check engine light. I went on it hard several times and nothing, just a healthy running(but loud) engine. I think my misfire was either due to the old O2 sensors that were replaced, or the exhaust leak. Any thoughts? I hope this in some way helps others troubleshoot their misfires.

 

I have a crack in my exhaust also and have a cylinder one misfire. My train of thought would think that if you have an exhaust leak around the flang, and it caused a misfire, would'nt it be a sparatic misfire. Thats just what has lead me to believe my crack doesn't cause my isolated misfire. What do yall think? Then again i do have low compression in cylinder one. But if i didn't would an exhaust leak cause an isolated misfire?

 

i cannot remember if i did have a misfire, i don't think so, but it depends on where the crack is....my 87 xj had a cracked manifold at the combiner on the driver's side and i had no misfire issues until it was replaced...just leaking exhaust into engine bay and leaking noise.

 

So you had a misfire after you replaced the exhaust manifold?

 

sorry...i meant...no misfire issues before or after replacing manifold

 

These same problems just happened to me. I have had a complete tune-up in Feburary. Did a compression test and these we're my results

#6 100psi
#5 80psi
#4 85psi
#3 90 psi
#2 83 psi
#1 85 psi

My XJ has 160,000 miles on it, and I didn't warm engine up before testing. Normal compression is 125psi though isn't it?