fivendime

This isnt your normal rough idle situation. After the cherokee has been warmed up to about 220 and I shut it off, if I start it right back up or even after a min or two it will run very rough like its running on 4 cylinders. My guess is the coolant temp sensor for the computer since it only does it when it gets hot. If I wait and let it cool down just a bit then its perfectly fine. Could it be something else?

Blackcherokee290

I had (ithink) the same prob. Ran at idle for awhile, drove a bit, shut off. cool for a min then start, few sec later it feels like it wants to die but corrects before it does- really rough idling & it threw a P0303 for cyl 3 . it went away after awhile but i never fiqured it out.

funkle95xj

Sounds like you were dealing with the more typical version of the rough idle condition. The fact that your motor threw a code for cyl 3 sort of proves that. It is cause by a somewhat clumsy design that places your #3 injector VERY near one of your exhaust manifold runners. This causes the fuel in the injector to become heated far beyond normal. When you run the engine till hot, then shut it off, this excessive heat can cause the fuel left in that injector to vaporize, which in turn causes a rough idle till all that fuel vapor has been pumped out of the injector and the rough idle goes away. Obviously this doesn't happen during normal running conditions due to a constant flow of fuel, but once it is allowed to sit, it vaporizes.

A resonable solution for this is to wrap the injector in some sort of heat shield tape available at most parts suppliers. May as well do all of the injectors while you're at it, but it's that pesky #3 that is most likely the culprit. Sorry I've got no info for you fivendime, but maybe this will help you out blackcherokee...

Blackcherokee290

okay so i apologize for hijacking your thread but i just learned i dont have your issue.
- the auto shop told me it was a bad ignition coil and i smelled bs so i got a scanner and then it went away. ill try wrapping the injectors- thanks.

fivendime

I would think this could be my fix buy wrapping the injector. I thought it might be my temp sensor, but after thinking about it if i run the RPM's up just a bit it will eventually go away, in about 15 or so seconds give or take. Thanks for the idea! It only does it on the trail or after i've gotten it hot and then tried to start it again.

funkle95xj

Yeah, it really sounds like you may have this condition as well fivendime. It's super common with XJs and certainly seems alot worse than it is. Usually wrapping the injectors resolves this issue, but doing anything you can to reduce underhood temps (upgraded fans, hood vents, etc...) will only reduce the chances of these pesky heat related issues returning. Hope it works for you man!

Blackcherokee290

okay maybe i did have your problem hahaha.