Only happens after I get the jeep to running temp and turn it off. start it again, 3000 idle. turn off, then after a minute or 2 its fine again(sometimes takes a few tries)....any ideas?

 

Could be the idle air control

 

Try removing the idle air control and clean it with carb cleaner and re adjust the idle motor and reset it.

 

Haha, x3 on IAC valve. It is usually associated with high idle issues. Don't unplug it while jeep is running, it won't do mechanical damage, but it will throw off the cel with an inaccurate reading, making it more difficult to diagnose down the road. Also, with that said, go to a good shop with a code reader and see what it says. With the right diagnostic tool you can look at specific functions like how well/accurately the TPS and IAC are working..

 

make sure your coolant isn't low! that IAC valve has coolant running through it! low coolant flow in the IAC valve can cause the valve to raise idle higher than normal! seen this multiple times!

 

Coolant is at the right level, checked yesterday.

 

...really??... My 99s IAC valve sits on the TB, so having coolant in there means there is coolant in my TB, which means there is coolant in manifold and by proxy, the engine?? Also.. Why would idle AIR control valve have fluid in it? Either I'm lost and need to do some serious homework on my jeep, or there was a misstatement by someone...

 

Yeahhh... Coolant doesn't touch the IAC valve....

 

Yes sorry their not the same as Hondas

 

In some vehicles there is coolant going through the iac valve. When coolant reaches operating temp the idle will lower. This system is used on Honda vehicles. And the iac valve sits on TB and is near intake manifold. No coolant in engine.

 

If OP has a renix, it could be the relay for the stepper motor reset. This relay keeps power to the ecu after key off to reset IAC.

 

89 is a renix

 

Yeah I checked first. This relay is called the 'power latch relay', FYI.

 

Its the throttle position sensor. There's actually a tsb on it. Try adjusting it down a .02-.04 volts on the engine side. Play with the adjustment you will find the sweet spot. Just don't go toooo far. It affects your shift points.

 

If that were the case, it would always be revving high and drive horrible, wouldn't it? It doesn't sound like the ecu is hunting. Dunno, could be a combination of things I guess...