When i first start the jeep. It idles really well at about 1000 rpms. Maybe a misfire here and there but very little. As it warms up, the idle drops to around 500 rpms and the needle jumps alot. Plus the misfires increase and it idles rough. Ive checked vacuum leaks: none. Plugs are brand new champion copper. And no cracked head. My uncle whos a mechanic said maybe the MAP sensor or IAC. I also ruled in the CPS. What do you guys think? Its been going on for a couple of months. Its a 2000 I6 with 122000 miles if that helps. Thanks!

 

What about the coil? O2 sensors?

 

It isnt throwing a code for anything. And would those affect the rpms going down like that?

 

Sure. You can check, I think, the impedence on the o2. If you have a junkyard near you, I'd get two of the sensors including the coil and see if they make a difference. If so, buy a new one and replace.

 

Does the coolant get low for no apparent reason?

How do you know for sure that the head is not cracked?

 

I loose coolant yes, but i know its leaking from the freeze plugs. I changed the oil recently and there was no oil antifreeze mixture.