i need help diagnosing a problem with my xj, it seems to be fuel related i think, i started by replacing the fuel pump 3 times then my tps, map sensor and air idle control sensor and then my crankshaft position sensor but nothing seems to help, she will crank up and sounds just perfect but once it starts to heat up around normal temp she starts to spit and sputter then a few back fires and then dies out, anyone willing to help or got any ideas ???????

 

Assuming this is your 98?

I'd check for spark when this happens.

Two common causes of thermal (heat related) failure are the crankshaft position sensor and the ignition coil. You already replaced the crank sensor but NOT the coil.

If this happens ONLY when the engine warms and then the engine runs okay again when it cools down, the coil is the next thing to rule in or out. You could test the coil when symptomatic for primary and secondary resistances, or you could just try another one. Easy to swap.

 

CEL?

 

I have had a similar problem with my 96. it runs fine and when I turn on the ac a drive for a bit the engine warms up and then when I shift gears it has no power. I havent switched anything out yet just wondering if anyone had any ideas on it. I know the after 96 jeeps are different and mine is a five speed two door. I'm learning a lot about it but it just started happening out of no where

 

Sounds like your precatalyst o2 sensor. Your computer does not read it until the 02 sensor warms up. get the NGK one from napa because they are the OEM for jeep. U can run it for a short while with the new 02 sensor and if it does not work just return it.

 

Wrong! There is generally no return on electrical parts. (would be nice!)
Interesting point though, if if failed lean. I've heard they generally go rich though, but Idk. Anyway below is a link with some info, you might want to check the wires to the front 02.

Give it a tune up, check for codes, for a start. Not sure if you are saying it runs fine WITH the ac or without.

http://www.naxja.org/forum/showthrea...ht=sensor+test

 

I spent time with similar issues and it turned out to be the Ignition Coil. It was doing what the OP was stating but it got worse and more frequent until finally it would die after 30 seconds. New (quality) coil,...no more issue. Even a good coil is fairly cheap.

 

Unfortunately this newb jumped offline before solidifying a few things.. Being on my the portable device I can't access the info relating to year, etc. so im thinking we may be assuming wrong year? OP mentioned replacing the CPS, isn't this a per 94 feature? Idk, I just wanna make sure we are on the right track... So yeah, I noticed there was no mention of the o2's being replaced. That or like OP said, once the rig is up to operating temp. is when the issue occurs. So is it a heat soak issue on something? Other ignition and or starting components that need replaced?

 

Yea ,gets confusing eh? Said he has a 96. I've tried PMing newbie's to consider starting their own thread, but usually somebody else replies and it just get's worse! Anyway, noting the date can help.

 

Sorry everyone I have to be at work super early in the morning so I had to get off here. It seems to me the Jeep is getting hot. When it starts acting up I crank up the heat (which sucks because its warm now) and it starts driving ok once it cools down a bit. My jeep is a 96

 

i had similar issues a few months back. look for wear in the wiring that runs right by the intake manifold heat shield. the wires could be worn through and causing a short.

 

first thing i would do check for codes even if light not on soft codes can be stored.

 

Yea forgot to mention my check engine light is on I'm going to take it and have the codes ran this evening and see what they say.

 

Yep,...check engine light/codes should be on the "top 10" list.

 

as others have stated, when the engine is cold and in "warm up" mode the fuel system is running "open loop" which means it's not using the upstream O2 sensor to adjust fuel trim. once warmed up it goes into "closed loop" where the O2 sensor readings are sent to the PCM and it adjusts fuel trim according to the voltage signal the O2 sensor sends. I agree you need to start with the CEL odds are the PCM is already telling you whats wrong.