So i have the normal 4.0HO i6. In my 1994, my cousin just replaced head gasket and grinded the valves. But i dont think he set the idle right. How can i get my idle right so when i start it, i dont have to give it gas. When setting at a red light im at around 400 to 500 RPMS according to my gauge. Now my red cherokee is at around 800 to 900 when setting. What should i set it at how and how do i properly set it ?

There is no adjustment that you can do, it's controlled by the PCM and IAC (idle air control motor). You may need a new IAC motor.

hmm... Well what would cause me to get down so low on RPMS? ive actually had to put it in park, turn the key and restart it. from it dying on me.

New tps maby? Idk if that controlls idle speed or not.

Check out the Technical Write-Up/How to section there is a thread on cleaning your IAC ....May help you?