J.Adams722
New Member
Since this forum and thread in particular was instrumental in solving my own misfire issue, I thought I would post on my experience and what I went through. First, I recently bought a 2005 LJ with a 6-speed tranny with about 150k miles. Shortly after buying it (as it always happens) my check engine light came on, read the codes and it was a p0306 code. So I thought a misfire, how hard could this be to fix? My Jeep started laughing at me I think, especially as I began down the path of figuring it all out. My approach was start small and simple, then go from there. Mostly I followed this thread as directed and tried everything.
- So I ran to the store and bought new plugs after reading this forum and got the Autolite XP-985 plugs. Gapped them and installed them. Still misfiring....
- Ran back to the store and bought a coil rail (now I realize that a MOPAR one may be the way to go) but I just bought one off the shelf. Still misfiring.... Then I reinstalled the factory MOPAR one when the new one didn't work. Still misfiring...
- Rented a NOID light kit and tested the injectors, seemed normal, but swapped #6 with #1 anyway. Still misfiring....
- Performed a compression test, all cylinders tested normal and equal in value. Still misfiring.....
- Tested for manifold gasket leaks with both propane and spray cleaner, found none. Still misfiring....
- Cleaned the throttle body and IAC valve, some crap in there but it really wasn't that bad. Still misfiring....
- At this point, I am thinking it must be something either very random or serious. So instead of throwing parts at it, I took it to a friend's shop to take a look with all the special tools and such. He retested everything I had done and found no problems with the above tests that I did. Then he used a dial indicator and found that the exhaust lobe on the cam was worn down significantly. Problem solved! Or so we thought, note Jeep is still laughing at me. So I had the shop install the new camshaft and check the head and everything. The cam was definitely worn down and needed to be replaced. This also accomplishes replacing the intake/exhaust manifold gasket which is on the list. So after the cam was replaced it did seem to run better and smoother. But you guessed it STILL MISFIRING....
- So then we replaced the crankshaft and camshaft position sensors. Still misfiring....
- At this point the shop has given up and I thought I'd bring it back and keep trying things. Cause all this while the Jeep ran fairly well. But still misfiring....
- I was talking to my neighbor one day, and telling him all about my woes of trying to fix a "simple" misfire. He mentions that he has a nephew who works for Chrysler and has been involved with Jeep engineering over the years. The nephew's son is also training to be a mechanic at this time. So my neighbor said he could put me in touch with them and see if they could help me. Their suggestions came back to look at all of the above things. But also to check all the wiring harness and connections to make sure there is no shorts or anything. And I had done that and all seemed normal to me. But I rechecked again and everything still seemed normal.
- But it made me think with all the PCM issues on these years of Jeeps, could it be that? These jeeps do have an individual circuit on the PCM for each injector, so it would be possible that particular circuit went bad. Checked and my Jeep has a factory refurbished PCM on it already. So I am now thinking at this point of dropping the money to get a new PCM from Wrangler Fix. But as I am twiddling my thumbs on that one....
- I got new H4 headlights and was cleaning the plugs off with electric connection cleaner and thought maybe I should hit the PCM connections. So I did, let them dry out. Plugged it back in and haven't had a misfire since that point!!!!! That was about 3-4 weeks ago and I have been driving the Jeep a fair amount to try and feel more confident that it is actually fixed. Now my Jeep is happy and content and purring like a kitten. Now my family and I can enjoy the Jeep as it was intended, out and about exploring this great open world we live in. And in between those times with my family, I can spend countless hours addressing all the other little issues I find or want to improve upon...