Engine Vibrates When Turning the A/C ON | A Stuck IACV

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The idle air control (IAC) valve is part of the throttle body in most fuel-injected vehicles. It works with the ECU to achieve smooth idle. Since it bypasses the throttle body and pipes air straight to the engine, it can modulate how much air the engine gets without working the throttle body.

If the IAC valve is stuck open, it will cause the engine to idle at a higher RPM. The engine would bog down and may result in the engine vibrating or stalling when running a heavy electrical load or turning the AC on or putting the car to ‘DRIVE or ‘REVERSE’.

SYMPTOMS:

• irregular idle speed
• engine vibrate
• engine stalling
• engine won’t start
• poor fuel economy

TOOLS:

• contact cleaner
• clean rag
• gloves
• face shield

PROCEDURES:

• remove the IAC valve
• rotate the stuck internal component until it rotates freely
• done