Is it fuel injected?
I would check the idle air by pass port. Its a control that opens and closes to let air by pass the throttle plate controlling the idle speed.
It could be dirty. It's bolted to the throttol body. You will need to get a replacement gasket but it won't cost much. I would also remove the throttle body and clean that as well. You will need a gasket for that too.
These are cheap parts and easy fixes.

It may not solve your idle problem but it can't hurt.