I've searched the forums and got some great information on this code but I'd like to run it by you guys as it's odd how this popped up.

Last week I changed the brakes, did an oil change and replaced the belt on my '01 Sport. After that happened my check engine light came on. Hooked it up and tested it to get the code and she throws a p0306.

One other thing of note, while cleaning around in the engine bay my buddy broke the pcv elbow on the back of the valve cover, we bought a new one and replaced it.

So using logic I'm trying to figure out why she's throwing a p0306. I came across an article to check the belt, I did and it had too much play. Tightened that down, cleared the code and 65 miles later p0306 is back. She doesn't seem to run rough. I do have the 0301 head but have not noticed any coolant loss since I've had her (knocks on wood). And to think I did all that work right before taking her in to get inspected...now I can't until I clear this up.

Thoughts?

P.S. It may be time for a new exhaust, I believe I may have a cracked exhaust header...she's had a ticking sound since I got her over a year ago. Would that cause this?

Thanks!

Edited: Spelling

 

For any single cylinder misfire, the spark plug and fuel injector need to be ruled in or out. As well as the connection with the coil rail to that spark plug. Replace the spark plug (be sure gap is .035) and if that doesn't help, swap the fuel injector from #6 to a different cylinder and see if the misfire follows.

Cracked exhaust manifolds are common on the 4.0 and should be addressed, but this would not likely be related to your misfire.

 

I've been chasing this exact same code problem for the last 6 months.
I have changed, swapped, and massaged everything I can that everyone tells me to do and then done it all over again.
EXCEPT replace the CPS and replace the Valve springs. Apparently there is a TSB on this. However it does not mention my year of XJ (2000).
I have now in my possession 4 new valve springs. With in the next couple of weeks now that somewhat warmer weather is approaching I will be replacing both springs on cylinder 6.
I will be posting if this works in this thread
https://www.cherokeeforum.com/f2/p03...t-stop-159990/
I hope it works. If not then I'm buying a replacement head anyways.
I'm keeping this Jeep!

 

Thanks for the tips. I will also keep this thread updated with what I've done. Probably won't get to it until the weekend though.

Obviously any other advice is welcome!

Thanks!