Hey guys I've got a 94 Cherokee with a 4.0 which has 145k on it. Just started having this issue where i start the jeep the rpms shoot up to about 2k and sit there until i put it in gear. And once it warms up it idles around 250-500 rpm.
I just changed the plugs, wires, distributor cap/rotor and its still doing it.

Any ideas what it could be?
Thanks in advance

 

Sound like either a bad TPS or IAC.

IDK if for the 91-01 years if ya got to adjust the TPS or not but when my other 89' had high idle, I replaced the tps, adjusted it and rpm was steady at 750 at idle and around 700 in gear.

 

Thanks man, ill try changing those tomorrow and see if that does the trick

 

Don't go changing parts without being sure, try this first....if you don't have a chilton manual I would say get one....

I have a renix jeep (87-90) my tps has to be .17 of my input voltage when the throttle is closed....so 4.89x.17= .82.

You have an OBD jeep. So im sure your testing procedure might be different...someone who has your era jeep should chime in soon I would think.

 

Maybe try using the search function here on the forum. Its helped me a lot since joining 4 years ago.

 

Clean your IAC first, you might not even have to buy a new one.
Clean your throttle body and valve
Check for intake/vacuum leaks

 

I dont have a chilton manual or a voltage meter. But i will try cleaning the IAC before i buy any parts.
I already checked for vacuum leaks but no such luck.
Ill grab some throttle body cleaner tomorrow

 

Has your mpg dropped? If so, you may have knocked a vac line completely off. This little guy might be the issue.

 

The gas mileage is soo bad on this thing i don't even bother recording it. Just checked-that little vacuum line is still attached, the cause of the bad mpg would be caused by the 33's/4.5in lift without regearing