Mitsubishi Repair: 93 Eagle Summit Wagon, 2.4L 4 Cyl, AWD, manual, max air flow, stepper motor

Question
A recurring issue with rough starting (usually when cold & wet).  Cars starts up but idles very low & will stall if gas pedal is pressed.  Once car warms up, the idle stablizes & car will run.  However, while driving car,it occaisionally loses power completely.  After pulling over, it will generally start up again either immediately or after a few minutes.  It does seem to be associated with wet (snowy) weather.  Car runs fine in summer months.  It's been in the shop several times but they are stumped.  Items recently replaced:  oxygen sensor, iginition coil, timing belt, water pump & spark plugs.  Also, shop tried replacing computer but it did not help so they took it back out.  Any suggestions?

Answer
Jen,
Stalling and a rough idle can be caused by a faulty idle air control (IAC) motor. This stepper motor receives a signal from the car's computer to allow a specific measure of air into to the intake to keep the idle speed constant to prevent stalling and racing.  The IAC is also referred to as the Idle Speed Control (ISC).  It's attached to the throttle body, and it's normally supposed to be open (allow max air flow) when you first start up the engine, and the engine is cold.  But if the IAC is attempting to adjust the idle when the engine is cold, it will cause the car to stall.  Cold and wet conditions can enhance the problem.  Have your mechanic test your IAC.  It can be tested while it's on the car and they should know the process to check it.
Good luck!