I have a 1989 Jeep Cherokee with a 4.0L and auto. Anyway my idle is all over the place in park it can be anywhere, after warmed up, from about 900-1600 RPM and it has the same fluculations in gear too.

Also, I have to crank the engine awhile in order start the vehicle and it doesn't matter if the vehicle is warm or cold. The fuel pump was changed today because of low fuel pressure and it runs much better after replacing that but it will still take a bit to start the old thing. Once it is running though it runs like a champ.

 

sounds like your IAC is bad or really dirty

 

what does IAC stand for?

 

IAC= idle air controller it controlls how much the throttle plate needs to be open for proper idle, its on the side of the throttle body

 

Thank you for your help.

Every little bit I do this Jeep makes it run better and better and it ran well when I first bought that thing. I absolutely love this thing.