How to Replace an Idle Air Control Valve in a 2001 Chevrolet Tahoe

The 2001 Chevy Tahoe base model came with a 4.8-liter v-8 and a four-speed automatic transmission. The engine's idle speed is controlled by the idle air control valve, which is located on the driver side of the throttle body at the front side of the engine. If your IAC valve seizes, or otherwise rendered inoperable by the computer, the engine speed will fluctuate randomly. Replacing the IAC valve is well within the realm of the home mechanic, but there is a idle speed learning procedure that has to be followed to properly pair the computer with the new valve.

Instructions

Park the vehicle on a level surface and set the parking brake and release the hood latch. Lift the hood and support it with the hood prop rod.

Follow the air intake tubing to the throttle body on the front of the engine. Examine the driver side of the throttle body and locate the IAC valve, it will be the top most sensor.

Squeeze the locking tab on the IAC valve wiring harness and disconnect it from the IAC valve. Remove the IAC valve mounting screw with a torx bit socket and ratchet. Grab the valve firmly and pull it straight out of the throttle body. Remove the IAC valve o-ring by hand, if it was left behind on the throttle body.

Compare the faulty IAC valve with the new one, they should be identical. Measure the distance between the tip of the pintle -- the small pin within the IAC valve -- and the valve's mating surface, it should be 28 mm or less. Push in on the pintle enough to shorten the length to 28 mm at most with your finger.

Install a new IAC control valve o-ring onto the new IAC valve. Apply a coat of fresh engine oil to the new o-ring. Position the new IAC valve in the throttle body and align the screw hole with the hole in the throttle body. Apply a coat of loctite 262 to the threads of the IAC valve mounting screws. Install the mounting screw and tighten to 27 inch-pounds, using a torque wrench. Connect the wiring harness to the new IAC control valve.

Sit in the vehicle and turn the air conditioning controls to the off position. Set the parking brake and start the engine. Allow the engine to warm to normal operating temperature before continuing. Manually hold the engine steady at a slightly elevated speed while warming up, if necessary.

Allow the engine to idle without any other input for five minutes, once it has reached operating temperature. Hold the brake firmly and shift the transmission into Drive. Hold your foot on the brake and allow the engine to idle for five minutes.

Shift the transmission into park and release the brake. Allow the engine to idle for an additional five minutes and then shut of the engine. Start the engine after 30 seconds and check for proper idle; if the engine does not idle properly repeat the idle learn procedure again.