Why Your Car’s Idle Air Control Valve Is Broken

Of all the things that can go wrong with your vehicle, the things that go wrong when it’s not even … Continued

Of all the things that can go wrong with your vehicle, the things that go wrong when it’s not even moving can be the most frustrating. This is the case when there’s something wrong with the vehicle’s idle speed, which is the engine’s default operating speed when the vehicle is sitting still. When something goes wrong there, the car’s idle can range wildly instead of settling into a steady-state, or it can just stop running altogether.

The maestro controlling this symphony of idling is the idle air control valve (IAC). Many vehicles today have IACs that are designed to “just work” for the life of the car, but that’s not always the case. Let Car Bibles walk you through some of the finer points of IACs and how they work. Let’s jump in.

How Does The Idle Air Control Valve Work?

Your car’s idle air control valve helps maintain the speed of the engine while it’s at idle by regulating the amount of airflow entering the engine. The valve is controlled by the engine control unit, which can adjust the idle speed to accommodate varying conditions, such as engine temperature.

What Are The Signs Of A Failing Idle Air Control Valve?

When your car’s IAC starts to fail, the problem can manifest itself in a variety of ways.

  • Stalling Engine

If the IAC flames out completely, the vehicle might be without a source of air to hold a consistent or proper idle. This can cause the engine to stall during operation, or to not idle at all.

  • Uneven Idle Speed

As the IAC fails, one of the most common signs of its demise is the engine’s idle speed. Once you turn the key or press the button, the vehicle should start up and settle into a somewhat even idle after its initial roar to life. If the valve is failing, the engine’s idle speed may go sideways with it, which can result in an abnormally high or low idle speed. In some cases, the idle may climb and fall as there’s nothing to regulate it.

  • Check Engine Light

A check engine light on its own can mean almost anything, but in combination with the other issue here, it’s a good sign that there’s a problem with your idle air control valve.

Idle Air Control Valve Failure Causes

The IAC is designed to last for the entirety of your vehicle’s lifespan, but there are a number of things that can cause it to fail. The most common issue is that the actuator can become jammed with dirt or other debris.

How To Resolve A Broken Idle Air Control Valve

Unfortunately, the best way to repair a broken idle air control valve is just to replace it. This is especially true with newer model vehicles, where the units have been designed to stay closed and are not serviceable or able to be cleaned.

Car Bible’s Glossary for Idle Air Control Valves

Get educated.

  • Idle

Idle refers to a vehicle’s engine that is running while the vehicle is not in motion. Each vehicle and type of vehicle will have a different idle speed, which is measured in rpm, or revolutions per minute.

  • RPM

Revolutions per minute, or rpm, is a term that describes the number of rotations that the engine’s crankshaft makes in one minute.

  • Throttle

The throttle is a component in an internal combustion engine that controls engine power by regulating the amount of air or fuel. The driver controls the throttle with the accelerator or gas pedal.

  • Stall

When a car stalls, it means the engine has stopped running for one reason or another. This is most likely to happen in vehicles with manual transmissions because they require the driver to maintain control of the clutch and transmission at all times. A bad IAC can rob an engine of enough air or fuel to stay running, leading even vehicles with automatic transmissions to a stall.

  • Backfire

A backfire occurs when combustion occurs outside of the combustion chamber, usually somewhere in the exhaust system. The unburnt fuel is ignited and can make loud sounds, even without the flames many imagine.

Your Questions, Our Answers on Idle Air Control Valves

Let’s answer your burning questions.

Q: Can I Drive With A Broken Idle Air Control Valve?

A: It might be possible, but driving with a failed or failing IAC is certainly not a great idea. Something about a stalling engine and a wacky idle doesn’t sound appealing.

Q: How Much Does It Cost To Fix?

A: On average, it’ll cost you somewhere between $200 and $500 to fix your failing IAC valve. Labor won’t be the big kicker here and should land somewhere around $100. The big costs come with parts, which can run upwards of $500 in some cases.

Q: Where Can I Find My IAC?

A: Well, the IAC is located on the throttle body in vehicles with fuel injection. Each vehicle is different, so you should check your repair manual to determine its exact location.

Q: How Hard Is It To Fix?

A: Replacing an IAC isn’t the most difficult job in the world, but parts of the process will involve disconnecting wiring harnesses and working with the battery, so if you’re someone that is completely inexperienced it’s a job best left to the pros. Besides, it’s not the pro-level labor that makes the job expensive, it’s the parts.

Video On Idle Air Control Valves

Car Bibles’ editors understand that not everyone is a text-based learner. For those kinesthetic people out there, we have your back with a video showing you exactly how hybrid cars work. We pulled it from one of our favorite, and most trusted, sources and it’s a great additional resource.

Car Bible’s Favorite Idle Air Control Valve- Related Products 

You can buy tools for IAC valve issues at almost every auto parts store, as well as online stores like Amazon. You have a sea of options to select from. We picked a handful of great parts and tools that can help you identify problems, and even replace the IAC valve if you’re so inclined. They’re cheap, reliable, and did we mention cheap? Check them out.

Idle Air Control Valve (model-specific)

Innova CarScan Pro OBD2 Scanner

Evil Energy Throttle Body Assembly (model-specific)

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