Engine idle problem

My old 87 GN with high miles has been idling poorly as of late. When I start engine, it will idle normal for about 30 seconds, then will drop off and shut off if I don't keep gas to it. Once it does warm up enough to idle without me putting gas to it, it still goes up and down. Anyone knows if this problem is caused by one of the sensors or prom?


Retired member
Assuming iac and tps are adjusted correctly, I would remove the iac valve and clean it with throttle body cleaner. Also spray out the throttle body while you are at it and wipe it out with a rag.