Chevrolet Repair: 90 lumina, massair, vacuum leak

Question
Hi I have a 90 lumina w/ 3.1 it will start and run smooth as long as you keep on the gas. It will not run in idle, I replaced the ECM,and the main computer, checked the map sensor and the massair, still will not run in idle. Any help would be appreciated thank you

Answer

GM IAC motor Hi,

 YOu need to check the IAC valve.  The IAC is a metered bypass vacuum leak around the throttle plates used by the computer to maintain a targeted idle speed.  IE The ECM target is 900 RPM and engine RPM is 1100.  The ECM will EXTEND the IAC pintle stepper motor to lower the bypass rate in effect lowering idle.

WAyne