I have a 1988 2.3 5 speed the rpms are fluctuating between 200 an 2200. its started this on Friday but it ran fine Saturday an Sunday an then it did it again Monday. it also its puffing a lot of black smoke when this is happening an wILL cut off sometimes an does not want to start back if I let it sit for thirty minutes to an hour it will start back but it will either be ok or go back to the rpms fluctuating. HELP PLEASE I DONT KNOW WHAT IT IS!!!

 

Idle air control valve probably stuck and can't regulate idle. Pull it off and clean it the stick it back on and see what happens.

 

its a vacuum leak. the black smoke is from the excess fuel the rpm fluctuation just comes with the territory of those two problems.