How Do I Fix a Car Idle Problem?by Alibaster Smith
A car idling problem can cause intermittent stalling and make it difficult for your engine to operate properly. A low idle may cause the IAC valve, or idle air control valve, to overcompensate for an improperly adjusted throttle. Of course, your IAC valve might be the problem itself. Before you can know what you need to fix, you should troubleshoot the problem. Fixing your idle problem can normally be done within an hour.
Open the hood of your car and locate the idle air control valve on the backside of the engine on the throttle body assembly.
Unplug the electrical connector running to the valve.
Unscrew the screws that hold the idle air control valve to the throttle body assembly and pull the valve off the throttle body.
Turn the valve over and look at the sensor wires. If there is any dirt or debris in the sensor, then spray the sensor wires liberally with electronic parts cleaner.
Set the dial on your voltmeter to "OHMs".
Touch the red lead of your voltmeter to one of the terminals on the end of the sensor and the black lead to the other terminal on the other end of the sensor.
Check the reading on the voltmeter. The reading should be "0" but a variance of ".05" is acceptable. The numbers represent the continuity in the sensor. The lower the number, the better.
Reinstall the valve.
Start the engine.
Turn the nut on the throttle cable at the throttle body clockwise to tighten the cable and increase the idle to 800 RPM. If the idle fluctuates, you may need to replace the IAC valve. However, your idle should hold steady if the valve's continuity in step 7 was within specifications.