Sensor Troubleshooting: Idle Air Control Valve

Checking & replacing the IAC

As we've mentioned in other articles, many of us freak out when the Check Engine/Service Engine Soon light illuminates on our car's instrument panel. Most people don't realize that many computer-recognized problems are faulty emissions-system sensors. You don't have to be a professional mechanic or have a degree in electrical engineering to diagnose and fix sensor problems, especially in older vehicles (i.e., ones that have outgrown their warranties). One component that falls into this category is the Idle Air Control (IAC) valve.

Idle Trouble

The IAC helps regulate the amount of air that enters the engine at idle. If the computer senses that the IAC isn't doing its job, a trouble code will be stored and the Check Engine light will illuminate. Using the proper scan tool, the trouble code can be "downloaded" and then deciphered by the scanner's instruction manual or by consulting a comprehensive service manual for your vehicle. If the code indicates an IAC problem, the fix is usually straightforward, as the Steps in the photo gallery show. You can often adjust and even replace the IAC in less time than it takes to drop off and pick up the vehicle at a service station. Find out what vehicles qualify for the government stimulus, Cash for Clunkers program.