Idle Air Control Motor IAC Replacement

Step 16 - Then, reinstall all electrical connectors to the throttle bore and idle air control motor.

Reinstalling Electrical Connectors

Step 17 - After installing all vacuum, coolant and electrical components position the air intake tube for reinstallation.

Reinstalling Air Intake Tube

Step 18 - Reinstall vacuum and transfer hoses to the intake tube, then tighten the mounting clamp.

Tighten Air Intake Tube Mounting Clamp

Step 19 - Once the air intake tube has been reinstalled, continue to install the remaining vacuum lines.

Installing Remaining Vacuum Lines

Step 20 - Idle air control valve installed job complete, double check all work and clear any codes that have been set, refill any coolant that has been lost.

Idle Air Control Valve Installed

Helpful Information

The idle air control motor or idle speed control motor is designed to adjust the air flow into the intake manifold at engine idle. Engine idle speed is monitored by the PCM which commands the idle air control motor to close or open to achieve the desired rpm. The air bypass port in the throttle body is used to feed the idle speed control motor. When an idle air control motor malfunctions it can cause the engine either to idle too high or too low, or stall the engine all together. This condition will usually illuminates the check engine or service engine soon light.

After the job is complete and the engine has been started, it can take some time before the idle air control can recalibrate itself, engine stalling, high and low idle are normal until a few run cycles are completed. Occasionally is it necessary to hold the throttle open long enough for the computer to take over control of the valve.

Note: On some Ford vehicles the idle air control motor to will create a "moaning" or "honking" sound when failed.

Best Practices

  • A condition called "coking" is a normal occurrence of a thin build up of a tar like substance which┬áis a normal by-product of processing large amounts of air. When this condition is present it must be cleaned with carburetor cleaner and a shop towel. After removing the idle air control motor open the butterfly plate and clean along with idle air control inlet and outlet passages.


Written by
Co-Founder and CEO of
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2014-06-27)