Is there a diagnostic link you can hook a scanner or code reader so you can see if any trouble codes are stored?

Check for a bad vacuum hose to the map sensor. Could be a throttle body that is sludged up causing the idle speed motor to try and compensate.

A good scanner hooked up the computer would let you see a data stream of all the sensors and what they are doing.

Might check other vacuum hoses to see if one is cracked.