Chewdog167

Ok this is my best description of a long standing problem I've had on an 01' xj. Once it gets good and hot the 6th cylinder will misfire, or if it doesn't while running it will on a hot restart. I've replaced the ignition coil, I've tested all the injectors with a noid light, I replaced the number 6 injector and thought I had it fixed. With the injector replaced I still had a code EVAP "small leak" which shouldn't create a drivability issue or was under the impression it wouldn't. I know there's a number of things that might cause a small EVAP leak and it's on the list to fix. But after driving about 175 miles and after a few hot restarts it began to misfire again.. Once it's cold and restarted it won't do it again till its hot or restarted hot.

I'm not sure what's going on or what tools I need to diagnose this problem. I bought this jeep with an over heated motor and a cracked head, the whole cooling systems been gone through and the head replaced. When all 6 are firing it runs strong, I have not done a compression test or a fuel pressure test yet, I'm wondering if they would help in this case or not. It ran last for a couple of hours before producing the problem and did so at a half tank of fuel. Before replacing the injector it would only take going around the block and restating the motor to produce the problem. I drove it all over town starting and stoping filled up the tank and drove it up north 140 miles the following day wheeled it and had fun for a few hours that evening. While on the trail the next day about two hrs in the problem came back from a hot restart after taken a break for a while.

Does this sound familiar or make sense to anyone? Please any input would be helpful.

NiteDog

I went through the same symptoms on my old 01 XJ. Changed head and intake. Did a smoke test replaced all leaky vacuum tubes and narrowed it down to the purge valve on the evap system.

Good luck

mikesignal

sounds like you have the typical "heat soak" misfire. usually it's on 1&3. You have to decide for yourself on how you want to fix the issue--
install an override switch for your electric fan
install a timer on your electric fan to run the fan after you turn the vehicle off for a set amount of time--this is what I did
install hood vents to let the heat out
install a cowl hood to let the heat out
wrap the injectors and fuel rail with heat sheath or tape--I prefer to not use the tape, but to secure the sheath with wire ties

one or more of these should fix your misfire after a hot start

on your evap leak you need to do a smoke test like Chew said, but before you do that you can check the green cap on the evap, the one next to the a/c dryer--make sure it's on there tight. Visibly check you evap lines. You might get lucky and find something.

tjwalker

You need to. These two tests are very basic and easy to perform. This is a process of elimination and a "testing based strategy" is always the best way to proceed.

Chewdog167

This is all pretty good stuff to get started on, I've never heard of a heat soaked motor. I think it does this pretty easy to be heat related but I'll do some experimenting. Gonna hit auto zone for some rental tools like the fuel pressure and compression tester. I will give the jeep some attention this weekend and hope for the best. As for the smoke test you have to take it in to someone don't ya? I know the kinda of smoke I'm smoking aint gonna show me **** but the munches.