How To Replace Idle Speed Control Motor IAC

Idle Air Control Motor IAC Replacement

Car Idle Motor Replacing Procedure

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 is 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.

Step by step guide on how to replace an idle air control motor valve. This article pertains to most vehicles equipped with a non electric throttle bore, appearance will vary but the procedure is similar.

Difficulty Scale: 3 of 10 Tools and Supplies Needed

• Socket Set
• Wrench Set
• Screwdriver set
• Shop Towels
• Protective gloves and eyewear
• Replacement Idle Valve
• Carburetor Cleaner

Begin with the vehicle on level ground engine off (cold) with the emergency brake set.

Step 1 - Locate and remove the air intake bore which is attached to the throttle bore and is usually done be loosening the mounting clamp. (Note: some idle air control motors can be replaced without removing the throttle bore.)

Remove Air Intake Boot

Step 2 - Once the air intake has been removed proceed in removing all vacuum lines from the throttle bore. TIP: Snap a quick pic from your phone to avoid confusion in reassembly.

Removing Vacuum Lines

Step 3 - After vacuum lines have been removed, locate and disconnect the sensor and idle air control electrical connectors. Be gentle with these connectors because they can be brittle due to under hood conditions.

Removing Electrical Connectors

Step 4 - Next, slowly remove the radiator cap to relieve system pressure, then locate and remove all coolant hoses connected to the throttle body.

Removing Coolant Hoses

Step 5 - Then, remove both the throttle and cruise control cables from the throttle body.

Remove Throttle Cable

Step 6 - Once all coolant, vacuum hose and electrical connectors have been removed, remove the throttle bore mounting bolts.

Remove Throttle Bore Mounting Bolts

Step 7 - After removing all throttle bore bolts, gently pry the bore loose from the intake manifold. The idle air control valve is attached (bolted) at the bottom of the bore.

Throttle Bore - Idle Air Control Valve Removed

Step 8 - Once removed, hold the unit in a vise to stabilized the valve for removal.

Idle Air Control Valve

Step 9 - Using an impact screw driver to remove the idle air control valve mounting screws.

Removing Idle Air Control Mounting Screws

Step 10 - After the screws have been removed, gently pry the idle air control valve off of the throttle bore, be sure to remove the gasket as well, match up the old valve to the new unit.

New Idle Air Control Valve

Step 11 - Using a shop towel and carburetor cleaner wipe all gasket surfaces clean to ensure a proper seal. Then, install the new idle air valve to the throttle bore, reinstall and tighten the mounting screws.

Installing New Idle Air Control Valve Motor

Step 12 - Next, gently reinstall the throttle bore making sure the gasket surface is clean, keep hoses and wiring clear from the mounting surface.

Installing Throttle Bore

Step 13 - After reinstalling the throttle bore and tightening the mounting bolts evenly, reattach the coolant hoses with clamps.

Reinstall Coolant Hoses

Step 14 - Once coolant line are connected, reattach the throttle cable assembly by installing and tightening the mounting screws.

Reinstall Throttle Cable Assembly

Step 15 - Next, Reattach all vacuum lines to the throttle bore. 

Reinstalling Vacuum Lines

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