Mitsubishi Repair: rolling idle, throttle body, idle speed control

Question
95 Galant.............2.4L.....I have a rolling idle after car gets warmed up. I have tried to clear codes by dis connecting battery.  Once re-connected I allow it to idle for 5 minutes. The check engine lite does not come back on for several hours. When the rolling idle starts again.   My question is,,,, What possible driveability component may be at fault?

Answer
John,
A rolling idle (or idle surge as some call it) is typically caused by a faulty Idle Air Control (IAC) motor.  This is also referred to as an Idle Speed Control (ISC) motor.  This little motor is connected to your throttle body and has the job of keeping your engine idling steady when at a stop.  When the IAC starts malfunctioning, the motor just starts guessing at where your idle should be set.  So, that's when the idle starts rolling.  Have your IAC inspected and replace it if necessary.
Good luck!