Updated on July 31, 2023
The idle air control – or IAC – valve is an important component in a car’s engine. Often the IAC is attached to the engine throttle and its purpose is to regulate the airflow in the engine, helping to create smoother idling.
However, issues with the IAC valve can lead to big problems with your engine. The valve is responsible for managing the airflow while the throttle is not being used when the engine is idle.
If this airflow is not controlled correctly, this can lead to stalling, poor acceleration, and the engine light illuminating. In this article, we discuss how you can tell if there is a problem with the idle air control valve and share our guide on how you can easily reset the IAC.
You can reset the idle air control (IAC) valve by turning the car on, putting the car into park, pressing the brake down, then pushing the gas pedal down, counting down about 5 seconds, turning the car off, waiting 10 seconds and start the car again, checking to see if the car is idling properly.
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What Is An Idle Air Control Valve?
The idle air control valve is an engine component, often found attached to the throttle body. The IAC works alongside a vehicle’s ECU to electrically manage the engine airflow when the car is idling.
The throttle plate closes when a car is idling, and to ensure the vehicle continues to run smoothly when it is stopped, the IAC valve continues to inject air.
The IAC works by bypassing the closed throttle plate, the valve allows air to circulate inside the car’s combustion area and allows the vehicle to idle smoothly.
The ECU also plays an important role in this process. When the car is parked or stopped, the computer system will then send a signal to the IAC valve. Once the valve has received the electrical signal, the valve will adjust to allow the required airflow into the combustion area.
How Do I Tell If My Idle Air Control Valve Is Bad?
As you can see, a fully functioning IAC valve is important for your engine’s overall performance. The valve will keep the correct amount of air circulating when the car is idle and the throttle plate is closed.
However, occasionally you may notice your car is not idling as smoothly as it used to or your check engine light is on and you don’t know why. These are just two signs that your idle air control valve is bad.
Let’s take a look at some of the other symptoms of a faulty IAC valve:
- Rough idling (car engine doesn’t feel as smooth when you are stopped).
- Poor acceleration.
- ‘Bursts’ in idle speed – the speed randomly fluctuates when the engine is idle.
- Stalling.
- Increased RPMs when the vehicle is idle.
- Check Engine light is on.
It is important to know the signs of a malfunctioning IAC as if your car is not idling correctly, you may end up with serious engine damage. However, it is also important to note that the symptoms listed above can also be signs of other engine issues.
It is always best to seek professional advice if you are concerned about the IAC valve. A professional diagnostic will reveal the true cause of your car’s issues, but you can try and test and reset your IAC valve yourself – keep reading to find out how.
How To Reset IAC Valve – A Step-By-Step Guide
If you notice your vehicle is displaying signs of a faulty IAC valve, you will need to troubleshoot and check it is definitely the idle air control that is causing these problems. Before rushing to reset the IAC valve, first, you can perform a quick test of the valve to see if it is working correctly or not.
Here is a brief guide on how to perform the IAC valve test:
Step 1
Turn both the radio and air conditioning off, you want to be able to hear clearly.
Step 2
Listen carefully to the car engine as it sits and idles.
Step 3
Note down the vehicle’s RPMs. This figure should be no lower than 600 and no higher than 1000.
Step 4
If the RPMs are low, this can indicate that there is a problem with the IAC valve or there may be a vacuum leak in one of the vehicle’s systems.
After testing the IAC valve, if an issue is detected you can try to reset the valve. Resetting the valve is not a permanent fix but it may be enough to keep your IAC working until you are able to get it repaired or replaced.
Resetting The IAC Valve
If you want to try resetting the IAC valve, here is our easy to follow step-by-step guide
Step 1
Turn the car to the ON position.
Step 2
Put the car into park (P) and press the brake down
Step 3
Now press the gas pedal down slowly.
Step 4
Once you have released the pedals. you can now just leave the car in the ON position for approximately 5 seconds.
Step 5
Next, turn the car off and leave it off for approximately 10 seconds.
Step 6
Finally, turn the car back on and check the vehicle is idling correctly.
How To Clean IAC valve
An IAC valve may not be performing correctly because it is dirty and is in need of some cleaning maintenance.
During combustion, carbon and debris can settle on the IAC valve, and this can build up over time. When contamination builds up inside the idle air control valve, the IAC may become faulty and not work as it should.
Cleaning away any built-up debris or contamination can help you to reset the IAC valve back to working order. It is important that you check your car owner’s manual when you intend to clean the idle air control valve.
You will not want to cause any further damage and the owner’s manual should provide you with accurate information on how to correctly clean the valve.
However, if you can’t find the relevant information, here is a step-by-step guide that should work with most vehicles when cleaning the IAC valve.
Remember, not all carbon cleaners may not be suitable for all vehicles and components and you should only use these products if you are confident they won’t do any harm.
Step 1
Locate the idle air control valve. In most vehicles, the IAC can be found near the air intake at the side of the engine.
Step 2
Next, remove the electric plug located at the back of the IAC valve. You should be able to use the plug by just using a screwdriver.
Step 3
Now you will need to remove the screws and bolts that have been inserted to hold the valve in place.
Step 4
Once the bolts are removed, you will now be able to access the valve that should be pointing downwards.
Step 5
Spray a carburetor cleaner onto the pointed end of the valve. Try not to get any of the cleaners into the valve’s housing as this may cause damage.
Step 6
Continue to spray the valve until you can see all of the carbon and debris has come away.
Step 7
Put everything carefully back into place, remembering to fix the wiring and plug it back.
Step 8
Once everything is reinstalled correctly, you can now start the car and listen to how it idles. If dirt was the issue, you should now notice an improvement in the sound.
This guide explains how to clean the IAC valve by removing it. If you want to learn how to clean the idle air control valve without removing it, there are several guides available online.
Are you more of a visual learner? Here is a video tutorial that shows exactly how you can clean the IAC on a car that is not idling correctly:
FAQs
How do you check a bad IAC valve?
It is always best to seek advice from a mechanic if you are concerned about parts of your car’s engine. However, you can test the IAC valve yourself, all you need to do is turn the car on and listen to the engine while you are stopped.
If the idling sounds erratic, too fast, or too slow, there may be an issue with the valve. Also, you will need to note down the RPMs while the car is idling, if this number is not between 600 and 1000, there may be a problem that needs addressing.
You can also try locating the IAC in the engine and checking for any build-up carbon or dirt that may be causing it to stick and not perform correctly.
How do you test the IAC valve?
To test the IAC you need to turn your car on and listen to the idling engine. A fully functioning valve will sound even and smooth, you shouldn’t notice any ‘bursts’ in sound or speed. It is important to be aware of the symptoms of a bad IAC valve, these include stalling, poor acceleration, increased RMP, and fluctuating idling.
What happens if you unplug IAC?
You can unplug the IAC and it should not cause any damage if you disconnect it while the engine is idling. However, the IAC valve plays an important role in keeping air flowing in the combustion when the engine is idling and there is a risk that removing it may cause some adverse effects.
Can the idle air control valve be cleaned?
Yes, you can clean the idle air control valve. The part can be cleaned by either removing it from the throttle body or in place.
You must be careful with the cleaning products you use to try and remove the carbon and debris, as certain products may cause more harm than good. We have shared a step-by-step guide on how to clean an idle air control valve in this article.
Conclusion
The IAC valve is an important component in a vehicle’s engine. The idle air control valve regulates the airflow in the engine combustion when the car is idling. When you stop your car and the engine is running smoothly, that’s thanks to the IAC valve.
Whilst the valve is designed to last your car’s entire lifetime, sometimes damage and debris can cause issues. If you notice your car is not idling as it should, there may be an issue with the IAC valve.
In this article, we have shared how you can reset the IAC valve and clean it to get it back into working order. If you are still facing problems when your car is idling, it may be time to head to the mechanics.
Check out these other related articles for more tips:
Why Does My Car Start Out Rough Then Smooths Out?
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What RPM Should My Car Idle At?