Idling problems

My Jeep has had problems idling for quite some time now but I finally decided to do something about it.

One evening after getting home I tore the air intake off the car to check out the IAC valve.

The IAC controls the idle of the engine when the foot is off the accelerator and the computer needs to mix a precise amount of fuel and air to keep the car running while at idle.

Air intake box atop throttle body
Air intake box removed, throttle body exposed. The IAC valve is bolted usually on the drivers side of the throttle body near the rear.

My IAC valve attached using one screw but was fused in place by 14 years of carbon deposits. It took a LOT of persuading for it to come off. I really thought I might break it while pulling on it as hard as I did but eventually it pulled loose. Use pliers if you have to but be very careful to not destroy the electrical connector which has a plastic housing.

Idle air control valve (IAC)
Inside view of IAC
Carefully remove O-rings. I used a fancy pick. A toothpick or screwdriver would do.
Brush gently (or not so gently if you have a decade plus of carbon deposit) make sure you use a good cleaner that is generally designed for this type of stuff. I chose throttle body cleaner.
Still a little to clean out
Clean as a whistle. Reverse the process and start it up.

You can also just replace the IAC altogether. Some cost more than others. Ranging from ~30 to $90. If you have a BMW it’s probably a cool grand and requires 14 special tools and a computer to install.

If you replace the IAC with a new one, the computer in the vehicle is going to need to “relearn” the fuel / air mixture curves. Your car is very smart and does this type of calculus on the fly. However be prepared. If you don’t reset / relearn the sensor with a scan tool, your car is going to have to learn while driving and the first 5 minutes or so your car is going to run terrible while it sorts things out.

Happy cleaning! Hope your car runs better!

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