Why does my IAC engine run at high idle speed?
Why does my IAC engine run at high idle speed? Cold weather can trigger this problem, and it usually corrects itself once the engine is warmed up. The IAC motor works with a vacuum port to control the engine's idle speed. By opening and closing a valve to the vacuum port at set intervals, the IAC motor sets the idle speed. What to do when your car is at high idle? While observing the valve with a flashlight, turn the key to the "ON" position, (DO NOT START ENGINE.) the valve should move slightly. Step 3 - Engine vacuum is...