up and down

i have a 1987 olds cutlass ciera 231 v6 3.8.The problem ive been having is the idle keeps going up and down.It will run just fine(about 1000 rpm)at idle.Then it drops to about 750 rpm and just about dies for about 30 seconds then it will pick back up and idle back to normal for a while -about 5 minutesand do it again.The check engine light also keeps coming on and off..??..ANY ADVISE WILL BE GREATLY APPRECIATED..THANK YOU. ALAN

There are several items that you need to check. First check for vacuum leaks. If you have a cracked or damaged vacuum line then it will cause wandering idle and the CEL to come on. If you don't find any vacuum leaks, check and clean the idle air control motor. Next check the mass airflow sensor and clean it with some electronics cleaner. Allow both to dry completely before you reinstall and don't touch the pintle on the iac or the inside of the mass airflow sensor.