Common Signs When The Idle Air Control Valve Goes Bad

Whenever you see the check engine light on your car glows constantly, there is a possibility the idle air control valve is facing a problem. In this article, we will show you some possible and common signs of a faulty idle air control valve.

The idle air control valve (or idle control valve) is an important component of the engine, which could be found on most of the car models these days. This unit is often located in the car’s throttle to make sure that your car would idle smoothly by regulating and controlling the flow of air which comes in the engine.


Most types of idle control valve are designed with a motor which is built in some areas on the intake manifold of your car. This motor or valve is regulated by a control module of the engine, which would change the idle speed based on parameters, including electric system load and engine temperature.

In case this control valve goes bad, it would immediately lead to many problems in your car. Thus, in this article, we have outlined some potential causes as well as common symptoms of a defective idle air control, so that you could deal with this problem correctly.

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Variation in The Idle Speed​

This is probably one of the most common signs of a problematic IAC. In general, most of us know that when we accelerate our car, the RPM of the engine will also increase, and once we step the gas off, this number returns slowly to the usual idling speed.

Nevertheless, when the RPM gets below the average level, which is about 800 RPM in most vehicles, it is highly likely that there is a problem with the IAC valve. In some cases, this valve would be clogged or near the replacement age. So your car would stall rather than idling after releasing the throttle.

The Idling isn’t Smooth

The most important purpose of an idle air control valve is probably ato make sure that your car would idle smoothly. Nevertheless, this function would be rough with a defective IAC valve. In these situations, you will notice shuddering or heavy vibration when you are idling your vehicle.

Also, there would be no or very little flow of air coming into the engine. This would make your vehicle vibrate, shake, and might also cause a loud sound when idling. Because of this uneven idling, you would notice that the vehicle will immediately stall when you run the car’s engine for next time.

Perhaps your vehicle’s IAC valve would be blocked with carbon gunk, and thus it would not open large enough to allow the air to coming in the engine.

Engine Stalls Because of Load

In normal condition of idling, your car would still have a smooth idling even when you turn the heater or AC on. Nevertheless, when the idle air control goes bad, your engine would stop suddenly as you turn up the heater or AC (the load) on the idling engine.

Also, you would also face a drag with the steering wheel after switching on the AC. To restart your car’s engine in these cases, you need to turn the load off and wait in a couple of minutes so that the engine would cool down, then crank it up again.

Light of The Check Engine is Turned On​

In fact, the most apparent symptom of a malfunction in the engine is the shining of the check engine light, which is situated on the dashboard of your car.

This sign means that there are some possible problems with your car’s engine. In these cases, you should use an OBD2 scanner to check the error code.

To do this, you should connect a scanner to the connector of an OBD2 that is located on the side of the driver. After that, turn on the key, and allow the scanner to analyze your car. If it gives a code with 11 errors, then an issue is occurring with your IAC valve. You could change this old unit with the new one if cleaning does not resolve your problem.

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How to Know if The Idle Air Control Valve is Still Healthy?

You could check the condition of an IAC valve by seeing its resistance. To do this, you should connect the ohmmeter with pins 3 and 2 of the valve while disconnecting the IAC.

If you receive the value from 10 to14 ohms, it means that the valve is working correctly. Now, connect with pins 2 and. If the resistance value is from 10 to14 ohms, you need to replace the IAC valve.

The Solution

  • After checking to know that the IAC valve in your car is defective and requires repair, the best solution instead of replacing, is to clean it thoroughly by removing and spraying throttle cleaner. As a result, the carbon debris that is clogged in this part would come off. Nevertheless, remember to get rid of any excessive fluid that remains inside the IAC valve.
  • If the problem is still happening even after the process of cleaning, you should replace with a new valve.

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2 thoughts on “Common Signs When The Idle Air Control Valve Goes Bad”

  1. Hi- I have a 2006 Mazda 6, 91,000 miles. It has been well taken care of. up to date on everything. I just installed a new battery, new struts a new thermostat and ecg sensor. I was just in for an oil change last week and was told everything looks good. This fall I went to a shop and asked them to look for a gas leak as I smelled some gas fumes periodically. The mechanic said he went thru my car with a fine tooth comb and found nothing! I changed my air filter as it was dirty and the problem stopped immediately! at that time my battery, only 2 years old died and no one knew why…so I bought a new one. once the battery was put it I noticed my car stalled once at a stop sign. No problems since. Then on Dec 26th I went to an indoor power car wash. then went to meet a friend at a restaurant. When I left the lot I noticed my interior lights weren’t fading off like they usually do when I start my car. I figured maybe some mechanism failed or froze because of the powerwash I had done on a 0 degree day. I had the trouble for a couple of days and it was wearing down my new battery so I went to get it checked at Mazda. They tell me its a bad body control module and about a $600 fix! they also ran a scan on my car and found a spark plug drenched in oil and a bad gasket cover??? also a bad air in take valve and a bad pvc…pvr valve??? Anyway the whole shebang is going to cost me $1800 to repair at this mazda store. I’m thinking that I am forced to got here since the module thing may need re-programed or something?? I was hoping to use my car at least another 2 years and use the equity in my car to get a new one. Now I don’t think I can sell my car like this. I know trade in values are always really low. My intentions have always been to sell the car. Now I am forced to go car shopping. Do you recommend I invest in fixing any of this and keeping the car, or fixing it to sell? or try selling it as is? I really don’t think one of the things that need repaired can be eliminated. it sounds like it all has to be fixed asap??? Your help and opinion is much appreciated!

  2. My ’03 Navigator stalled recently while coasting toward a stoplight at about 45 mph. I pulled over and stopped, then attempted a restart during which the vehicle started and ran as though nothing happened. A week later, it stalled again, this time while coasting around a corner in-town at about 25 mph. This time, the vehicle would not restart. At one point, I was able to run the engine with the aid of the starter, but it died as soon as I backed off the starter. Now, it will not start or fire at all.

    Question: can an IAC valve fail completely, causing a no-start condition?


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