so last night i cleaned the throttle body and replaced the cap, rotor, plugs, and wires. the idle is smoothed out quite a bit, but the odd thing is that is has a high idle after i drive it. when i start it up, the idle is good, about 800rpm in park and about 650rpm in gear. but after i drive it some, the idle jumps to about 1200rpm in park and about 1000rpm in gear. something to do with the tps maybe? thanks

 

The IAC could be sticking.

 

yep id check that first^^

 

Best to remove the IAC and clean it when doing a TB cleaning. be careful with it and don't pull or twist the pintle. Just clean it up with a q-tip.

 

ok, thanks. i am new to the jeep world, so where is this sensor? somewhere around the flex tube im guessing

 

It's not a sensor. It's the Idle Air Controller. Looking into the engine bay you will see the throttle body. There are two attachments on the front of the TB. The one on the left is the IAC. The one on your right is the TPS.

 

I read a lot of posts about idle speed and wonder about my XJ. Mine idles about 1200 which everyone seems concerned about but in my case my 94 XJ seems to idle its smoothest and quietest at that speed. Usually you can't even tell it's on it's so smooth at 1200 RPM. On those times it has gotten down to the 800 range it seems as if it's struggling and about to stall out. It's been like this since I got it 10 years ago.

 

Have you ever cleaned your TB and IAC?

 

ok to use carb cleaner on it with the q tip?

 

I guess. The point is you don't want the engine to ingest carb cleaner unless it specifically states "oxygen sensor safe" on the can.

 

ok, im not going to clean it with the motor running, everything will be all dried up before i start it up again. just didnt know if the controller was ok with carb cleaner. hopefully this helps otherwise ill just order a new controller

 

IAC doesn't care about carb cleaner that's not oxygen sensor safe. The oxygen sensor does though.

 

well, cleaned it pretty good, still get the high idle. new sensor for my 1990 cherokee then? im hesitant cause i have read about people getting new IACs and the high idle remains.

 

High idle AFTER it warms up?

Sounds like a vacuum leak.

The O2 sensor senses it's too lean and adds fuel. Then the total mix is too much - runs faster.

Do the smoke test to find the leak.

Blow cigarette smoke through a hose into the intake manifold. Use a rag or tape to put over the top of the throttle body to keep the smoke in. Look for where it leaks out where it shouldn't.

 

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