That depends on what year his car is. Newer Northstars use an Idle Air Control (IAC) system rather than the Idle Speed Control motor. The difference is the newer IAC is a variable air bypass valve straddling the throttle blade that is always fully closed at idle. The ISC system is a servo motor that forces the throttle blade open at varying degrees to control idle speed. The IAC is a little more accurate and seems to be more reliable than the ISC servo motors, probably because it doesn't have to fight against the throttle return spring. I think the cutoff year is 1996. Anything '96 or newer uses the IAC system.Jimbad said:Check the Idle-Speed Motor (Solenoid). This was my problem when I had your symptoms on my Northstar. Replacement is basically not difficult but made nasty by the location of the small mounting screws and nuts. Keep a magnet handy!