IAC elimination

Common IACs found in Ford vehicles.

Almost every modern fuel injected vehicle includes an IAC (idle air control) valve. This valve controlled by a solenoid or stepper motor regulates the air flow during idle when the throttle body is closed. The IAC creates an bypass around the TB (throttle body) and is often mounted on the intake manifold or throttle body. Because air density and fuel atomization changes with different temperature and conditions, the computer opens up the IAC valve more and allows for greater air while the car is cold. Upon reaching operating temperature or at least operating for a few minutes to warm up the internal components of the engine, not as much air is needed and the computer brings the IAC valve back to it’s normal more restricted position.

IAC designs can often be complicated in wiring and function, making them less desirable to keep for custom applications. They can be seen as an unnecessary complication to make cars more user friendly. For those who wish to simplify their vehicle and don’t mind the extra manual operation eliminating them is a simple task. There are multiple ways this task can be accomplished:

1. Threading: If the ports for the IAC valve are round then usually tapping them and putting in threaded brass plugs is a simple and easy solution.
2. Epoxy putty: One of the easiest and most reliable approaches is to purchase epoxy putty from any auto parts or hardware store. It comes in a stick with clay like properties, that contains a second type of epoxy on the inside. Upon mixing the two, the epoxy heats up and hardens. This gives someone a few minutes to make sure it’s pressed into the passages as hard as possible and to smooth out te exposed areas. It can be sanded and painted as well, ensuring a clean finish.
3. Flange plate: One can also create a metal plate to encompass both of the openings, drill the necessary holes for the bolts, and use some silicon and/or gasket material to create a good seal.

Example of IAC elimination.

Once the passages have been sealed, all one has to do is bring the car up to operating temperature and adjust the throttle stopper screw carefully to find the best setting for idle. The screw should have threadlock on it so once the adjustments are made it will not move. The reason this has to be done after the car has warmed is that the engine requires more air when it is cold, and while something may seem fine when the car is cold the idle will climb dramatically once the car is done warming up.

The only downside to eliminating the IAC besides setting off an engine error code is that the driver will have to apply a slight amount of throttle during warmup, on most cars even after 30-60 seconds of running the engine will be warm enough internally to use less air through the TB. The throttle adjuster screw may also require re-adjustment during drastic temperature or altitude changes, however from the testing performed throughout the entire year in southern United States, no adjustments were needed of any kind.