My niece’s 1997 Cavalier had an intermittent stalling problem. It goes worse over time, and I eventually borrowed her car to diagnose and solve the problem.
The pattern was fairly clear. Whenever I pulled up to a full stop and the engine began to idle, there was a chance the car would stall. All of my research pointed to a problem in the throttle – the part of the car that controls air coming into the engine.
After cleaning the main body of the throttle and replacing the Throttle Position Sensor, the problem didn’t go away. This left one final potential culprit: the Idle Air Control Valve.
What and Where is the Idle Air Control Valve?
The idle air control valve (IAC) is a small component that controls air coming into the throttle body of your car. Normally, the air intake is controlled by the throttle plate, which is in turn controlled by the accelerator pedal.
When you pull up to a stop and idle, however, the throttle plate is closed. The IAC valve then opens to a certain point, allowing in a carefully calculated amount of air to allow the engine to idle properly. If this valve gets gunked up with carbon debris, which happens over time especially on higher mileage vehicles, the valve will either not open or it won’t open properly.
The result? Either a rough idle or, in my case, a complete stall. The valve wasn’t opening sometimes, completely cutting off the air to the engine and forcing it to stall.
On the 1997 Chevrolet Cavalier, this is on the back of throttle body. Stand in front of you car, and look under the hood. You should see a large air hose that connects to the air filter at one end (located in the front right) and to a big metal thing on the other end (in the center of the engine compartment, all the way in the back). That metal thing is the throttle body.
Remove that large air intake hose. There should be two screws holding down clamps. Remove those, and the hose will come off no problem. Be careful, though, it will be dirty.
This will reveal the throttle plate and the front of the throttle. You should see a large metal plate covering a large hole, and above that a much tinier hole. That tiny hole is part of the Idle Air Control Valve.
On the back of the throttle body, you’ll see a small component that is attached by two screws. It has a wiring harness plugged into it. This is the IAC valve. You need to take it out.
Unfortunately, it’s in a crappy place to get to. You need a hex key or hex bit for the screw. If you have a small hex key, you should be able to reach in and unscrew the screws. I was able to go to Lowes and get a t-shaped screwdriver. It worked kind of like a ratchet, but it took a hex bit instead of a regular socket. Without it, I don’t know how I would have gotten in their and removed the IAC.
Cleaning It Up
Once you get the IAC removed, it’s time to clean everything up.
You’ll want something called Carbeurator Cleaner or Throttle Body Cleaner. You can use the two items interchangeably. There should be plenty of different types available at your local auto parts store or WalMart.
First, blast the IAC with a whole bunch of the cleaner. You should see some black gunk start to come off. Make sure you spray into the inside of the valve, where the spring is. I sprayed it four or five times, letting it dry a little in between, to get rid of all the carbon build-up. Keep cleaning until it looks clean.
The reason we removed the air hose was so that you could clean out the small opening the IAC goes into. Spray some more of that carb cleaner into the tiny hole at the top of the mouth of the throttle body. Make sure that hole is open and free from debris.
While you’ve got the hose off, you can also clean out the main throttle body. There’s a plastic covering on the left side of the throttle body that you can remove, allowing you to pull the metal lever and manually open the throttle plate. Then, just spray a bunch of the carb cleaner inside and watch the gook fade away.
When everything looks nice and clean, re-assemble. Re-attach the wiring harness and the air intake hose. Fire up the car.
Be warned! The car will start rough. This is the engine working through the carb cleaner and any gunk that went down the throttle. Let the car idle for five or ten minutes, and it should even out.