Symptoms of a Bad Idle Air Control Valve (IAC)

Common symptoms of a bad Idle Air Control Valve (IAC) and how to fix it. Read here for more information: https://www.backyardmechanic.org/symp...
An Idle Air Control (IAC) valve is controlled by the computer and allows air to bypass the throttle body butterfly plate.

Some Newer vehicles don't use an IAC but have an Electronic Throttle Body (ETB) System, which controls the throttle butterfly plate.
A bad Idle Air Control will only affect the idle of the engine, but engine will run well when the gas pedal is pressed.

Symptoms of a Bad Idle Air Control Valve
Idle Speed Erratic
Idle Speed Too High
Idle Speed Too Low (Stalling)
DTC Error Codes (P0505 to P0509)

How To Fix a Bad Idle Air Control Valve
An intake air leak can cause the same symptoms as a bad IAC since it is letting air in around the throttle body.
The most common fix is to clean the IAC of carbon build-up, but it may also have failed or have a wiring issue.
If the IAC is cleaned, the engine may run badly for 2-3 minutes until the cleaner is burnt away.

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