what is an Idle Air Control valve

An idle air control (IAC) valve regulates the amount of air flowing to the engine, when the engine is idling.

Having the right idling speed of an engine is vital to the economy and safety of the parts of the engine. While starting the car, a cold engine will require more air to idle smoothly. Also, when you step on the gas and then let off, the air supply to the engine ceases. But to ensure that the engine doesn’t jerk to a halt, a little air has to be supplied to the engine. From the above mentioned instances, it is clear that regulating air supply is vital for the smooth running of the engine. At the same time, the amount of air that enters your car’s engine should be kept under check, else the engine will have more air than fuel (hypothetical though!) This is where the idle air control (IAC) valve enters the picture.

 Now, let’s take a closer look at the purpose of idle air control valve, in this  Blog write-up.

How does an Idle Air Control Valve Work

 The idle air control valve is controlled by the Engine Control Module (ECM). The ECM is the monitoring module (or computer of the car) that keeps a check on the engine idle speed. The ECM uses the IAC valve to control the amount of air that is allowed to bypass the throttle intake plate, so as to keep the engine idle speed constant.

There are two idle settings in any vehicle. The minimum idle setting is done at the time of manufacturing itself, which allows a certain amount of air to pass through the valve irrespective of the IAC valve position. The running idle setting is achieved by the combination of IAC valve position and airflow.