What Happens When an Idle Air Control Valve Goes Bad

A bad idle air control valve is one of the most frightening vehicle malfunctions you can experience. When the part is wearing, it can cause your car to idle roughly and at times sputter out. 

It can happen anytime. So, this is something you should address as soon as you start to notice signs of a bad idle air control valve. Otherwise, you could put yourself, your passengers, and other drivers in danger. 

What is an Idle Air Control Valve?

On fuel-injected vehicles, the idle air control valve attaches to the throttle regulating the airflow and ensuring smooth idling. When the throttle plate closes during idling, the air control valve bypasses the plate injecting air, so your vehicle is smooth at stops. 

The motor needs air to burn fuel. When your car is in ‘Park,’ or you are at a stop. In modern vehicles, the computer sends a signal to the idle control valve. The valve adjusts to allow the correct amount of air into the combustion compartment. 

If all of the components are operating optimally, the idle is smooth. The RPMs fluctuate very little, and your vehicle does not make revving or sputtering sounds.

What Happens When the IAC Valve Fails?

AC284 Idle Air Control Valve

When an idle control valve goes bad, the initial symptoms may be mild. At first, you may notice that the engine feels rough when you are sitting at a stop sign or traffic light. The car may also sound different when it is idling. 

In severe cases, your vehicle may come to a complete stop in the middle of the street, and you may not be able to get your car to restart. A car with a bad IAC valve is more likely to stall in traffic when you are idling. Coming to a stop when cars behind are unaware that you are having car trouble creates a dangerous situation. 

If your vehicle stalls on the freeway, it is even more challenging to fix your vehicle. If you suspect that there is something wrong with the valve, please, try to stay off the highway. A stalling vehicle is dangerous anywhere, but it is even more critical when it happens on an interstate’s main lanes. 

Where is the Idle Control Valve?

Every vehicle make and model is different. So, you must check your owner’s manual to identify the exact location. On most vehicles, it connects to the throttle body beside the intake manifold, and it is usually in the middle at the top of your engine. 

If you are unable to identify it positively, you should enlist the assistance of a certified mechanic. Hiring a service technician to do the job for you is almost always less expensive than paying for a botched DIY repair. If you are determined to do it yourself, you may want to look at a video of someone fixing the same car make, model, and year vehicle.

You can usually find it by following the air cleaner hose to the top of the motor. Be sure to disconnect the battery before you work on the IAC valve or any other electrical component. 

Troubleshooting an Idle Air Valve

Idle Air Control Valve

When you notice that your IAC valve is not functioning correctly, you can do a few things before you replace the part. These tips may help you get your car driving to get home or to your mechanic shop. Or, the fix could be more permanent. Furthermore, if you plan to repair your idle air control valve yourself, you need to perform each of these steps anyway. 

Test Your Idle Air Control Valve

At times, the signs of a failing air control valve are apparent. However, depending on several other factors, you may not recognize that the part needs attention. So, you can perform a quick test to determine the health of your IAC valve.

Turn the radio and air conditioner off, and pay attention to the sound your car makes. Next, make a note of the RPMs. The RPMs for passenger cars should be no lower than 600 or higher than 1,000. 

If the RPMs are too low, it can indicate an issue with the IAC valve, or it could be a sign that your vehicle has a vacuum leak. When the RPMs are high, it is an indication that the IAC valve may need to be cleaned or replaced. 

Reset Your Idle Air Control Valve

Resetting your IAC valve can help to get your car going again. The valve pintle position is what controls the flow of air into your engine. If the pintle position is incorrect, the part will not function properly. 

So, you will need to reset the valve. To perform a valve reset: 

  • Turn your vehicle on. 
  • With your car in ‘Park,’ push all the way down on the brake. 
  • Then, slowly start to release the gas pedal (only allow the pedal to decompress slightly). 
  • Leave your car on for five seconds. 
  • Next, turn your car engine off, and let it sit for 10 seconds. 
  • Finally, turn your vehicle back on and check to see if it is idling correctly. 

If you have a drive-by-wire vehicle, you may not be able to start the car without resetting the throttle body valve plate. In that case, you need to follow instructions for resetting it specifically to your vehicle. Or, enlist the help of a qualified mechanic. 

Clean Your IAC Valve

Over time, carbon and other contaminants created by your engine during combustion can build up in the idle control. The debris can affect the functionality of the valve.

Cleaning your intake air control valve may help to get it working correctly. It is a reasonably simple task, and it will allow you to inspect the component. 

Before getting started, you need to check your vehicle manual to make sure that you can use carbon cleaner on your car. You will also need to gather the tools below: gather:

  • Automotive cloth
  • Wrench
  • Flathead screwdriver
  • Phillips head screwdriver
  • Carbon cleaner
  • A new IAC valve gasket. 

Then, you need to make sure that you take some safety precautions. For example, if you have recently driven your vehicle, you will need to wait until the motor cools completely. You may also want to wear work gloves and safety goggles because you do not want to get the chemicals in your eyes or skin.

When you are ready, you will need to remove the idle control valve (following steps 1 through replacement instructions below). Then, follow the instructions on the cleaner bottle and guidance from your owner’s manual. After you clean the components, follow the instructions for replacing the part and test your car. 

Clean Your Throttle Body

If your car is still idling rough, you may need to clean the entire throttle body. It is usually the case if your gas pedal is sticking. Carbon builds up inside the throttle body just like it does on the valve. 

When that happens, it creates a sticky carbon film on the throttle plate which causes the pedal to feel sticky. Cleaning the throttle body is a more involved process than simply removing the IAC valve and replacing it. 

You need to follow specific instructions for your year, make, and model vehicle. However, the necessary steps include: 

  • Detach the throttle body hose. 
  • Remove the air cleaner. 
  • Disengage the air control and position using the tabs on either side of the throttle body. 
  • Remove the throttle position sensor. 
  • If your vehicle has water lines, remove them. 
  • Disconnect the throttle body cables being cautious not to touch them to any other components. 
  • Unbolt the throttle body. 
  • Carefully remove to keep the part taking care not to damage the seal. 
  • Remove the seal. 
  • Follow instructions on your carb cleaner. 
  • Replace the parts. 

Replacing Your IAC Valve

If your vehicle is stalling, you likely have a bad valve. In that case, you need to remove the old valve and replace it. Replacing the IAC valve is a much simpler process than removing the entire throttle body and cleaning it.

Plus, the throttle control valve is a relatively inexpensive part. So, you might want to try replacing it before you clean the entire throttle body. Just be sure you clean the IAC valve seat when you return it, so the new part doesn’t get dirty. 

To replace the IAC valve: 

  1. Disconnect your battery cables. 
  2. Locate the wiring harness electrical terminal and disconnect it. 
  3. Take out the IAC valve.
  4. Clean the valve seat. 
  5. Replace the idle control valve and reconnect the wiring harness terminal. 

After you replace the valve, you may need to follow the steps for resetting it. 

What Is The Cost Of Repairing Your IAC Valve?

Idle control valves are relatively inexpensive. They range in price from around $30 to as much as $400. If you decide to take your vehicle to a shop, the labor will cost less than $100. When you do the job yourself, you also need a carb cleaner which is a few dollars. 

FAQs

Question: How do I fix my IAC valve?

Answer: The way you fix your idle control valve will depend on what the vehicle is doing. If your car is stalling, you will likely need to replace it. If your vehicle is just idling roughly, you might need to clean the IAC valve and the throttle body.

Your IAC valve should last for as long as you have your vehicle. So, it is more likely that you need to clean the part than replace it. However, on older vehicles, the valve may fail.

If you own a newer vehicle, replacing the valve may require advanced automotive knowledge. So, if your vehicle is relatively new, you should consider taking it to a certified automotive technician or dealership.

How do you reset your idle air control valve?

Resetting your idle air control valve might fix your problem. Here are the steps:

  1. With your car in ‘Park,’ press the acceleration pedal down all the way.  
  2. Decrease the pressure on the gas pedal slightly. 
  3. Start your car. 
  4. Run for five seconds. 
  5. Turn the engine off. 
  6. Leave off for ten seconds. 
  7. Start the vehicle without depressing the accelerator. 
  8. Check idle speed. 

Question: Can you drive with a bad idle air control valve?

Answer: A malfunctioning IAC valve can cause your vehicle to stall out in traffic. So, it is not a good idea to knowingly drive with a bad one. However, your car may operate, which can make it difficult to diagnose. 

When you drive your vehicle with an underperforming IAC valve, it can cause damage to other components, but it can also result in a deadly car accident. 

Question: What are the symptoms of a bad idle control valve?

Answer: Recognizing the symptoms of a bad idle control valve can help you prevent a dangerous stalling situation. Here are the most common symptoms of a bad IAC valve:

  • Check engine light comes on. 
  • Rough idling
  • Stalling
  • Weak acceleration
  • Fluctuating idle speed
  • Increased idle RPMs

Final Thoughts On Idle Air Control Valve Malfunctions

When your car is operable, but the idle is rough, you likely need to clean the valve. If your vehicle is not stalling and the gas pedal is sticking, you probably need to clean the body and valve. And, if your car is stalling, it is perhaps time for a replacement valve. 

Maintaining your throttle system requires you to clean, replace, or repair the components occasionally. It is always good to replace the parts or remedy any automotive issues as quickly as possible.

Otherwise, the part could damage others or cause the valve to stop working altogether, and you risk stalling, which is dangerous and stressful. 

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