Chey monte carlo 1998

Check your belts, make sure that they have proper tension on them and they are not overly worn and slipping. Then have your alternator and battery tested (you should do this even if the belt is bad, because a bad belt means bad charging and that can strain both the battery and the alternator). This should point you in the right direction. (or at least narrow down the possibilities).

I had that same problem and the mechanics couldn't figure out what was wrong...I took it to a firend and as soon as i pulled up it started reving on its own while in park. It was the idle air control valve that had to be replace.

It sounds like you either have a bad mass air flow sensor, or a major vaccum leak. Get a can of throttle body cleaner and spray around the intake and throttle body if you have a vaccum leak you will notice a significant change in engine rpm, even with a surge.