So, recently in the mornings (now getting colder in Massachusetts) when i go to start my xj to let it warm up before school i turn the key and it turns over but will not idle itself. its hard to explain. its like it starts..but it isnt telling itself to give it fuel and just dies. on the other hand when i start it and give it gas it stays running as long as i keep giving it gas. but as soon as i let go it drops to 500 rpm then stalls out. im hoping its a simple sensor issue that i could replace so i need your help! thanks.

 

I would have to say that most likely your problem is an air idle control valve (aka idle air control valve). This unit works like a choke for fuel injected vehicles. Without this unit your rig wont idle. The unit is on the top of the engine and only has two screws holding it on. Should only take five minutes to change.

 

i was hoping for something like that to be the issue and save me some money. i just thot it was weird how it will run when I give it gas. hopefully i can get some more peoples views on the issue and possibly order the part tomorrow.

 

The idle air control motor only works when you are not giving it gas. It allows air to bypass the throttle plate and keep the motor runing. When you give the jeep gas the throttle plate opens thus you are no longer using the idle air contol valve. If the valve is sticking shut no air can bypass the throttle plate and it wont idle. You can take the valve off and try cleaning it with an air intake cleaner. It might just be gummy and thats why is is sticking.

Another question have you tried driving it? Does it drive fine down the road and only gives you problems when you take you foot off the gas? If so the idle air control valve is most lickly the problem.

 

yes when i drive it, it is fine. and i just remebered that once the engine is warmed up a little (once the temp. gauge moves a little past 100) it can idle itself just fine and i can leave it alone. i cant believe i forgot to mention that before.

 

Ask a buddy to watch the IAC with your engine running. Turn your engine off, then switch the ignition off. The IAC should move a fraction of an inch to prepare for the next start by holding the throttle slightly open for that first gulp of air when you turn the key. If it does, and you are still experiencing the issue, I would suspect the throttle position sensor could be the culprit.