To check an idle air control valve, wait for the RPMs to drop, and test how your car responds to a tap on the accelerator. If the RPMs return to normal and then drop quickly, disconnect the valve from the vehicle. Connect a voltmeter and ensure that the resistance is between 10 and 14 volts.
- Perform an idle test
With your car running, be on the lookout for dropping RPMs — a common sign of idle air control valve problems. When the RPMs start to drop, lightly tap on the accelerator with your foot. Watch the RPMs as you do so; if they go back up to an appropriate level and drop again when you let your foot off of the pedal, it can be a signal of a valve issue.
- Disconnect the idle air control valve
Drive to your garage or driveway, turn the car off, and wait for the engine to cool. Disconnect the valve.
- Measure the valve resistance
Connect a voltmeter to the second and third pins on the valve, and look at the reading. If your reading is between 10 and 14, the valve is performing appropriately. If the number is lower or higher, you may need a replacement.