7 Idle Air Control Valve Symptoms and Solutions

Idle Air Control Valve Symptoms

You get in the car, the engine’s sputtering, and it sounds like you’re not going to make it out of your driveway. But as soon as you hit the open road, everything sounds fine. Your check engine light is still on though. So what is going on? Maybe is it bad idle air control valve symptoms?

These are all common symptoms of a bad idle air control valve. But what is an idle air control valve, what does it do, and how does it work? More importantly, how much does it cost to replace?

We’ll break it all down for you here and even walk you through the steps so you can replace it yourself if you want. Luckily, whether you choose to do the work yourself or plan to take it to the shop, idle air control valves are one of the easier and cheaper components of a vehicle to replace.

What Is an Idle Air Control Valve?

Idle air control valves, commonly referred to as IAC valves, do just what the name implies. They control the amount of air that your engine receives while it’s idling.

While you might think since your engine always idles around the same RPM, the inputs are always the same,but this couldn’t be farther from the truth. Different temperatures, air pressures, and oxygen makeups all affect how efficient your engine can run.

Furthermore, varying engine loads drastically change how hard your engine needs to work to idle at a consistent RPM.

As all these values change, your engine needs to accommodate accordingly to reach a steady idle. One of the key components that helps your engine do this is the idle air control valve. It regulates the intake according to your engine’s output and keeps everything running smoothly while you idle.

How Does an Idle Air Control Valve Work?

If you don’t know how a system is supposed to work when everything is running smoothly, you’re going to struggle to identify when things aren’t working correctly, not to mention how to fix the problem.

The idle control valve is a sensor that works in conjunction with other sensors throughout your engine. The vehicle’s Electronic Control Unit (ECU) receives inputs from sensors throughout the engine, and it uses those inputs to determine how much air the engine needs to stay within a specified range.

The idle control valve tells the ECU how much air the engine is currently getting, which the ECU uses to determine whether it needs to open or close the throttle body.

What are the bad Idle Air Control Valve Symptoms?

While there are tons of different ways an idle air control valve can present itself, we’ve highlighted the three most common symptoms below.

1. Check Engine Light

Your engine uses the check engine light to tell you about a wide array of problems. As soon as something goes awry, the check engine light illuminates to let you know there is a problem.

If your idle air control valve is faulty, you will get a check engine light – unless the diagnostic system is malfunctioning too.

If you do have a check engine light, you need to read the code. If you don’t have a code reader, take it to a parts store like AutoZone, and they’ll read it for free. If you have a faulty idle air control valve, the check engine light will mention the circuit.

2. Fluctuating Idle Speed/Rough Idle

Your idle air control valve regulates how much air your engine gets while idling. It’s supposed to adjust according to conditions to produce a smooth idle automatically.

If it’s not working correctly, it won’t perform this function properly, which can lead to either a rough idle or a fluctuating idle speed depending on the malfunction.

There are tons of different ways that an idle air control valve can break, and the severity of the fault will affect how much you notice a rough or fluctuating idle.

3. Engine Stalling

If the problem is severe enough, the engine might stall out entirely while it’s idling. This condition will worsen depending on the weather or when you turn on additional loads.

A specific condition might have your engine idling smoothly, but with a faulty idle air control valve, it won’t be able to adjust as those conditions change.

How to Repair a Bad Idle Air Control Valve

While you might be tempted to replace the idle air control valve immediately, the truth is that you can often fix the problem with a quick cleaning.

The idle air control valve is easy enough to get to, and if you’re able to fix it, then it’s well worth the extra time it takes to clean it.

When cleaning an idle air control valve, use a high-quality degreaser, and scrub the ends with a wire brush. You won’t be able to get the valve looking like new, but you’ll often be able to clean it enough to get it functioning correctly again.

Cost to Replace a Bad Idle Air Control Valve

The cost to replace a bad idle air control valve varies widely depending on what you drive. The cost of an idle control valve itself ranges between $50 and $100.

From there, labor costs range from $70 to $300. Combined, it can cost anywhere between $120 and $400 to replace your idle air control valve.

The good news is that it’s typically easy to get to and replace if you’re looking to save a little cash.

How to Replace a Bad Idle Air Control Valve (Step-by-Step Guide)

If you’re looking to save a little cash and are a bit mechanically inclined, you can replace your idle air control valve yourself. It’s one of the more straightforward repairs to complete, and we’ll walk you through everything you need to know to get the job done!

1. Locate the Idle Air Control Valve

It’s easier to find than you might think. The idle air control valve is usually near or on your throttle body or intake manifold. Once you’ve located the idle air control valve, you can move onto the next step.

2. Disconnect the Battery

Anytime you are working with electrical components, you need to disconnect the battery. Failure to do so can lead to a static charge that can damage more components and cost you a ton of money.

3. Gain Access to the Idle Control Valve

Depending on what you drive, you might be able to skip this step altogether. However, if you can’t reach the idle air control valve, then you need to remove any components that are obstructing your access.

4. Disconnect the Sensor

There will be an electrical connector you need to remove on the backside of the idle air control valve. Typically, you can remove these connectors by hand, but sometimes they get jammed and become difficult to remove. If this happens, a small flat head screwdriver can usually get the connector off – just be careful not to break anything!

5. Remove the Bolt

The idle air control valve is usually held on by two bolts. Remove these bolts and gently remove the old idle air control valve.

6. Install the New/Cleaned Idle Air Control Valve

Make sure to line up the bolt holes when you’re installing the new idle air control valve. Reinstall the bolts and reconnect the electrical connector.

7. Reinstall Any Removed Components

If you removed any components to access the idle air control valve, reinstall them now.

8. Reconnect the Battery

Since you disconnected the battery during the parts installation, you’ve already reset the engine control light. Once you reconnect the battery, you should be good to go!

Can You Drive with a Bad Idle Air Control Valve?

Sometimes you can drive with a faulty idle air control valve, while other times, it can cause further engine damage. Because of this, you shouldn’t drive with a bad idle air control valve, even if the problem doesn’t seem like a big deal.

While you might think you can avoid the problem by not idling, every time you stop at a red light or a stop sign, your vehicle is idling. The truth of the matter is there’s no getting around it.

So, while you might be able to drive with a faulty idle air control valve, it’s simply not worth the risk.


There’s nothing more gut-wrenching than a check engine light that you weren’t expecting. It feels like the worst kind of lottery when you’re reading the code. The worst results can cost you thousands, and the best can run about 20 bucks.

Fortunately, faulty idle air control valves are on the cheaper end of the spectrum, especially if you do the job yourself. Sometimes all you need to do is clean the idle air control valve to get your vehicle back out on the road!

When the fix might be free, why delay the repair and potentially damage your engine? Get your hands a little dirty and get your car running like new!

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