I've had these symptoms several times with fuel injected vehicles. If it is TBI fuel injection, the TBI unit needs to be removed and cleaned. Clean the idle air circuit and the butterfly, they are probably gunk'd up. Use throttle body cleaner and lots of rags. Remove the IAC valve and clean the pintle. Probably plenty of youtube videos to watch if unfamiliar. Install throttle body with new gasket. While it is apart, clean the mass airflow sensor MAF (if equipped) with spray electronic cleaner, both cleaners available at most auto parts stores.
