Idle problem

Hi and thanks for using 2CarPros.com.

The idle speed in park should be between 700 and 900. If your vehicle is looping, going up and down in speed without touching the throttle, chances are the idle air control valve is bad. Here is a link that describes the component and how to replace one:

https://www.2carpros.com/articles/how-to-replace-an-idle-speed-control-motor-iac

Also, an engine vacuum leak can cause an erratic idle speed. Here is a link which describes how to check for a leak:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

I am not sure which engine you have the 4.0L or the 4.7 V8. I have attached pictures of both engines so you can locate the idle air control motor. It will be mounted on the throttle body. Picture 1 is the V8 and picture 2 is the six cylinder.

I hope this information is helpful. Let me know if you have other questions or need more information.

Take care,
Joe