The idle air control valve is responsible for controlling the engine idle speed via the car's PCM (computer). These valves are configured differently depending on manufacturer but perform the same task. The IAC or ISC valve as it's called diverts engine intake air from the main throttle body and bypasses a portion of the intake air to control idle speed. When the idle speed cannot be controlled it will trigger a check engine light (MIL) due to idle speed fluctuations. On newer cars (2000 - 2005) depending on manufacturer this valve is being phased out as electronic throttle systems are becoming commonplace.
As a car ages the IAC will become dirty (a condition called coking) due to the volumes of air processed through the valve. Heavy particles in the air attach themselves to the valve's internal parts making it difficult for the valve to operate.
Idle Air Control
The idle air control valve (IAC) is located near the throttle body of the intake manifold in most cases. Additional designs include rubber hoses running from the throttle body and air intake tube to a remote valve.
The cost of an IAC will vary but typically will run between $60.00 and $120.00 US. If you are not changing the valve yourself labor costs will be minimal because of the easy access to the valve. If the valve is mounted to the bottom of the throttle bore such as in Toyota products the cost will run slightly more. To service the IAC separately the cost should be applicable to the vales location. Most services of this kind are included in a major tune up.
Locate the IAC valve on your engine. If your car does NOT have a throttle cable
you do not have an IAC valve, this is the best way to tell what kind of system your
car has. For this example we have removed the
throttle bore and cleaned it,
once completed remove the mounting screws to the idle air control valve. You might
need to use a impact screwdriver to get the screws undone.
Use carburetor cleaner to spray the valves internal parts using a shop towel
to help wipe away deposits (clean the valve thoroughly). This can take some time
so you may need to let the valve soak in cleaner depending on the level of coking
while other idle
air valves need to be replaced due to internal wear.
Please watch this video of the job being done, then continue down the guide to glean additional helpful information.
The IAC gathers air from internal ports inside the intake and throttle bore systems.
These transfer ports need to be serviced as well when cleaning the IAC motor to
help keep the newly cleaned valve working correctly.
Our certified technicians are ready to answer idle air control cleaning questions for free. We hope you saved money and learned from this guide. We are creating a full set of car repair guides. Please subscribe to our 2CarPros YouTube channel and check back often for new videos which are uploaded regularly.