Idle Air Control (IAC) Valve
What it is
The idle air control valve regulates how much air bypasses the throttle plate at idle, on engines with a cable throttle. (Drive-by-wire engines control idle through the throttle body instead.)
What it does
It opens and closes to hold a steady idle as load changes — for example when the A/C or headlights switch on. A sticking or carbon-clogged IAC causes a high, low or surging idle and stalling, and can set P0506/P0507.
Symptoms of failure
- Codes P0506 (idle too low) or P0507 (idle too high)
- Surging or hunting idle
- Stalling at stops or when the A/C turns on
- Hard starting
- Idle that will not return to normal
Common fault codes
Which vehicles need it
Cable-throttle engines (mostly pre-2008). Carbon build-up is the usual cause and often cleans up.
Replacement cost
| DIY (part only) | $20–$100 |
|---|---|
| At a shop (parts + labor) | $120–$300 |
| Replacement interval | No set interval — clean periodically; replace when cleaning no longer holds idle. |
| DIY difficulty | Easy (DIY) — a couple of screws and a connector; try cleaning first |
| Recommended brands | Standard Motor Products, Hitachi, Delphi, OEM |
Where to buy the part
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Frequently asked questions
Can I clean the idle air control valve instead of replacing it?
Usually yes — carbon build-up is the most common cause of idle problems. Remove the valve and clean it and the passage with throttle-body cleaner before buying a new one.
Why does my car stall when I turn on the A/C?
When the A/C compressor loads the engine, the IAC must add air to hold idle. A sticking or dirty IAC cannot keep up, so the idle drops and the engine stalls — a classic IAC symptom.