At what mileage should idle control valves be replaced?

There's no set mileage for replacing an idle air control (IAC) valve. They don't wear out in a predictable way like brake pads. Instead, they fail due to carbon buildup, electrical issues, or internal mechanical problems. This can happen at any mileage, from relatively low to very high.

Instead of relying on mileage, it's better to replace the IAC valve when it's malfunctioning. Symptoms of a failing IAC valve include:

* Rough idle: The engine shakes or vibrates excessively at idle.

* Stalling: The engine stalls, especially at idle or when stopping.

* High idle: The engine idles too fast.

* Poor fuel economy: A malfunctioning IAC valve can negatively impact fuel efficiency.

* Check engine light: The check engine light will often illuminate with a related diagnostic trouble code (DTC).

If you're experiencing these issues, have your vehicle diagnosed by a mechanic. They can determine if the IAC valve is the cause and replace it if necessary. Simply replacing it preemptively at a certain mileage isn't recommended, as it's unnecessary and wasteful.