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How to Test, Clean, and Reset Idle Air Control Valve?


There are numerous components and systems that keep your car in perfect working order at all times, even when it is only idling. The idle air control valve is one component that influences how smoothly your car can idle. A car’s air control valves are the least valued component. Most people downplay its significance.

So, if your car stalls or idles erratically, there might be an issue with the IAC valve. When this component breaks down, it may result in vibrations and major performance problems. In this post, we’ll go over the fundamentals of the IAC valve and how to test and reset it. But before that, let’s get an overview of the IAC valve.

What is Idle Air Control Valve?

Idle Air Control (IAC) valve helps in managing the engine’s idle speed in fuel-injected automobiles. At the same time, the Engine control unit regulates the working of the valve. The IAC valve regulates the flow of air past the shut-off throttle plate. To control airflow, it has a solenoid or valve-operating coil that opens and closes. Moreover, the electric current flowing through the solenoid controls how much air the valve can limit.

Since it is electronically regulated, the air can be kept at the ideal level and adjusted to changes in engine load. Only when you release the accelerator pedal, it takes control of the engine’s rotational speed. Therefore, when air movement increases, it causes a higher idle speed for starting.

What is Idling a Car?

When you don’t press the gas pedals, and your car engine isn’t accelerating, then it is known as engine idling. So, in simple terms, when you start the automobile in park mode, the engine is idling.

The engine’s idle speed is the rate at which it runs when the car is not receiving any acceleration inputs. The idle speed of the vehicle is shown in revolutions per minute (RPM). You can check it on the speedometer dashboard.

Depending on the vehicle, the standard consumer car will idle between 500 and 1000 RPM. For high-performance cars, it may start beyond 1000 RPM.

Why is IAC Valve Important?

The idle air control valve is one of a number of parts in your engine that affect how the engine idles. It helps in increasing and decreasing RPMs. The motive of the IAC valve is to maintain constant idle speed and prevent stalling once you release the clutch or brake. Due to a rigid throttle plate opening module, your fuel-injected engine can stall in case of variable load on the engine. So, there was a need for variable idle control.

With the help of electrical IAC valves, there was more efficient idle management. The motorized IAC valves can open or close the bypass to multiple degrees. Thus, it maintains a constant engine speed and enough power to avoid stalling.

How to Test the Idle Air Control Valve?

How to Test the Idle Air Control Valve

There are many ways to test your IAC valve. It can be done through:

  • Multimeter
  • RPM check
  • OBD scanner

Diagnose IAC Valve Through Multimeter

  • Locate the idle air control valve and take it out.
  • Set the multimeter to measure resistance.
  • In the next step, you should please use the red lead and black on different IAC valve solenoid terminals.
  • Read the resistance output of different IAC valves.

Measure the Idle RPM

The individuals can also test the IAC valve by measuring the idle RPM when the valve is in connection to the engine compared to when it is disconnected.

  • Firstly, start your engine. Read the tacheometer and find the stable idle RPM.
  • If there is unstable RPM, there is a fault in your IAC valve.
  • Now, remove the throttle and take another reading.
  • Restart your engine and take another reading.
  • Check for the difference in reading.
  • If the readings are the same, then there is a fault in your IAC valve.

Scan with OBD Scanner

  • Plug the OBD scanner below your car dashboard.
  • When you receive the P0505 error code, then there is a problem with the voltage supply to IAC terminals.

Symptoms of Poor IAC Valve

Your car may give indications of a problem with the idle air control valve in a number of ways. However, these symptoms are extremely generic and may not be a completely reliable diagnosis. A careful diagnosis is necessary before moving on, though, as the symptoms of an idle air control valve failure might mimic those of other component failures.

Difficulty in Starting the Car

If your car engine isn’t getting enough air, then it may not start or start slowly.  It can be a sign that the idle air control valve needs repair.

Rough Idling

Due to inconsistent air intake, the engine will create a hesitating and dying sound.


When the engine is not receiving the right air-fuel ratio, the engine fuel will be left behind even after the sparks. The remaining fuel will seep into the system and will cause a backfire. 

Car Engine Crashing After Start

The car could be able to start before it runs out of air and dies if the valve malfunctions intermittently or only sporadically operate during specific phases of its cycle.

How to Clean Idle Air Control Valve Without Removing?

You may have observed that cleaning the engine part is time-consuming. As it involves the removal of the component, you will need expertise, and it will ultimately reflect in the cost. But, in the case of the IAC valve, you can do it without removing it and saving time and money. Cleaning the IAC valve doesn’t require a lot of hands, and you can do it yourself.

  • You should first park the car and let its parts get cold.
  • Get yourself protective glasses and gloves.
  • Find the valve.
  • Remove the air duct and filter box for better reach.
  • Use the screwdriver to disconnect the clamps.
  • As you disconnect the clamps, you can see the throttle body and air filter.
  • Check the hole inside this component if you find a passage or hole in the throttle body.
  • It plays a crucial role in directing air from the air duct into the engine.
  • In this hole, a certain amount of carbon or other debris can quickly assemble. Therefore, you should clean it.
  • Clean the carbon build-up using the wire brush.
  • Reconnect the clamps, screws, and wirings.

How to Bypass Idle Air Control Valve?

It is a quick and easy process. Due to multiple problems in the IAC valve, your car’s performance will decrease.

  • Remove the ignition key and ensure that the car is off.
  • Find the control valve.
  • It is typically found on the intake manifold close to the throttle body.
  • Disconnect the idle air control valve.
  • A flat-head screwdriver should be inserted between the valve and the manifold’s body.
  • Use a flathead screwdriver to turn and open the valve.
  • Be careful not to harm the valve or the manifold. From the manifold, pull the valve apart.
  • Attach the bypass hose or fitting to the idle air control valve and the manifold.
  • To stop air intake, you can alternatively put a bypass plate between the throttle and the valve.
  • Reconnect the valve’s electrical connector.
  • Start the engine once to check the idle speed.

How to Reset Idle Air Control Valve?

If you have a car manufactured after the year 2000, then you can do it with your feet and hands. You won’t need any diagnostic tools.

Here are the quick steps to reset the IAC valve. These steps are good for Chevy, Ford, and BMW cars.

  • Firstly, push the gas pedals.
  • Next, start your car engine.
  • Run your engine for 5 to 10 seconds.
  • Now, turn the ignition key off.
  • Wait for a while and restart your car engine.
  • It would reset your IAC valve.

You can also go for the following steps.

  • Start your car and after a while turn the engine off.
  • Now, turn ON the ignition.
  • Press the accelerator 4 to 5 times.
  • Now, release the pedal.
  • Restart your car.

Follow these steps if you drive Cadillac, Chevrolet, Buick, or Oldsmobile built before 2000.

  • Put the car on the Parking brake.
  • Link the ALDL (diagnostic test terminal).
  • Launch the engine.
  • Maintain an engine speed of at least 2000 RPM.
  • After ten seconds, turn off the ALDL. Shorting pin A (ground) to pin B on the connector causes the vehicle to establish its default engine speed.
  • Take the earth up.
  • Turn off the ignition.

Frequently Asked Questions

Where is the Idle Air Control Valve Located?

The IAC valve is located under the bonnet of your car. However, the exact location varies according to the car brand and model. Usually, it is near the throttle body at the top of the intake manifold. It connects to a sensor via multiple wires.

What happens when the idle air control valve goes bad?

The engine’s airflow is restricted when the idle air control valve malfunctions. In that case, the engine stalls when the vehicle can’t get air.

What happens if you unplug the idle air control valve?

You can temporarily unplug the IAC valve to prevent it from identifying the idle speed issue. When you unplug it, you will find that there are no more changing idle rates.
However, it may also result in the engine running rough or misfiring, even though you appear to have a smooth start once more. Therefore, removing the idle air control valve may have a detrimental effect on how well the engine runs.

What can you do if your IAC valve is failing?

When you notice a problem with your IAC, then you can
●      Try resetting the IAC valve.
●      Clean the IAC Valve.
●      Replacing the valve is the best option to solve the malfunctioning issue.

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