Driving With A Bad Idle Air Control Valve – Symptoms & Solutions

How do you realize you're driving with a bad idle air control valve? Abnormal idle speed and engine stalling frequently are the most common symptoms of a bad idle air control (IAC) valve. Also, the issue appears with other symptoms that we'll discuss throughout the content.

The function of the IAC valve is to manage the engine speed when you keep your car at the idle point. This valve ensures and maintains quality airflow in the engine. But when it becomes defective, it can't manage the airflow quality, which affects the engine's functioning.

If you know the symptoms and solutions of the issue, you'd be able to prevent it. When you learn about the warning signs and their impacts on your vehicle, you'll never drive your car with a bad IAC valve. It's because driving with a bad IAC valve is responsible for some fatal car issues that lead to a hefty penalty.

So, you can't leave without learning the symptoms and possible solutions of a bad IAC valve.  Simply read on and prevent your car from potential internal crashes.

What Happens While Driving With A Bad Idle Air Control Valve

The Idle Air Control – IAC – valve controls the engine speed while leaving it idle. The IAC valve delivers essential rest to your engine when you leave it with power off.

But if this IAC valve becomes faulty, it loses control over the engine speed in the idle position. As a result, the engine runs strangely, and it indicates the issue with some symptoms.

The issue can trigger your car a sudden death by stopping working unexpectedly. You may be able to start it again, but the problem becomes severe very soon if you leave it without fixing it.

You'll get some symptoms of a bad idle air control valve that will ensure the issue. The symptoms are not the same for all cars. They may appear differently, but engine stalling and varying engine speeds are shared among others.

Also, the symptoms can include engine check lights and difficulty pressing the brake. Whenever you get one or more symptoms of this issue, you must take them seriously.

Moreover, it indicates the symptoms with varying idle speed, requiring more force on the brake pedal, illuminating Engine Check Light, etc. No matter the symptoms, a bad IAC valve isn't suitable for any car engine. 

How Does Driving With A Bad Idle Air Control Valve Impact The Engine?

Idle air control actuator or valve poorly impacts engine performance when damaged. You'll get your car with some odd behaviors if its IAC valve goes terrible. Indeed, your car will misbehave with indicative signs at the beginning of the issue.

The vehicle becomes more mysterious over time by repeating the warning symptoms. They make your car engine vulnerable, and you can have more problems with the engine.

When you continue driving your car with these issues, they'll damage the engine's internal components very soon. Even it'll prevent the engine from passing an idle air control valve test for a defective IAC with a check engine light.

What Are The Symptoms Of A Faulty Idle Air Control Valve?

Abnormal idle speed, halting, checking engine light, and requiring additional force to press the brake pad are significant symptoms of a bad IAC valve. Let's get the idle air control valve stuck open signs in detail with a summary table:

Abnormal Idle SpeedRepair/replace the IAC valve
Engine stallingRepair/replace the IAC valve
Check Engine LightScan & repair/replace the IAC valve
Hard to press the brakeRepair/replace the IAC valve
BackfiresRepair/replace the IAC valve
Harsher engine soundsRepair/replace the IAC valve

Getting Abnormal Idle Speed

A bad IAC valve shows its face with an abnormal idle speed. An unstable sluggish speed results from the inability to control your car's idle speed when you switch it off. The IAC valve has a specific program that helps the car to keep pace with its speed in a passive position.

A faulty IAC valve can't control the engine's idle speed. Therefore, the engine runs at varying speeds – either more or less than the programmed speed. It means that the rates can be higher or lower suddenly and frequently.

Now, the question is: what's the average idle speed of a vehicle? The regular idle speed of a passenger car is 600RPM to 1000RPM. But if it's a medium or heavyweight truck, its ideal idle speed is around 600RPM. Consult a mechanic to fix the issue, as it's impossible to solve without proper technical knowledge, practical experience, and essential tools.

The Engine Is Delaying & Stalling

Delaying and stalling your car while starting can be a good indicator of a faulty IAC. Your car engine runs smoothly when it gets a particular number of gasoline and air. Otherwise, the engine can't maintain the preset idle speed.

Sometimes, the engine suddenly stops working immediately after starting. When you find this symptom in your car, you must bring it to the dealer or mechanic to fix it. They know how to adjust idle air control valve, and they may need a replacement.

Glowing Check Engine Light On Dash

All components of your car, including the IAC valve, are under continuous monitoring of the engine control module (ECM). When the ECM gets any abnormal reading of engine rotations, it indicates the problem with symptoms, like checking the engine light on the dashboard.

The symptom or the issue typically doesn't stop a vehicle engine. But it'll be severe over time, which can cause other mentioned signs and problems. If you scan it, you'll get an error code. All these indicate an early fixing of the issue to avoid engine damage.

Demanding Additional Push On The Brake

An idle car engine is easy to press its brake pad. But it becomes hard and wants extra force for a bad IAC valve. For example, when you're at a traffic signal, you get the brake pad stiff to brake your car.

It usually happens for irregular revolutions of the motor for flawed IAC. You need additional strength to stop your vehicle when there is more RPM than the expected value.

This symptom clearly indicates a problematic IAC valve. So, avoid driving the car with this issue and bring it to the mechanic shop. They know how to test idle air control valve when it's malfunctioning. Thus, they'll fix the problem accordingly.

Having Vehicle Backfires

Getting flames from the exhaust pipe is another symptom of a faulty IAC valve. It may involve some other engine issues. But don't ignore it – especially if you get it with other abovementioned signs.

You can test it with accelerate and decelerate tasks to ensure the issue. If you get a leakage in the exhaust pipe after the test, it's likely to happen of a malfunctioning IAC valve. As a result, avoid further driving your car. Just take it to the mechanic shop to fix the issue.

Idle Engine Sounds Harsher

A bad IAC can make the engine harsher sound on idle. It's a rare symptom to be confirmed the issue of IAC failure. You can ensure the problem if you get some other symptoms with it that we've indicated above.

You must consult a mechanic to finalize and fix the problem when you find one, and one makes two. Never leave any indicating signs without treating them properly.

How To Fix A Faulty IAC Valve?

Follow the below steps to fix a defective IAC valve.

First Step – Disconnect The Electrical Wire

Remove the wire attached to this IAC valve. It has connected with the ECU.

Second Step – Remove The Bolts

The valve has two bolts on its two sides. Remove them with a spanner or wrench. When you unscrew them, you'll get the valve.

Third Step – Close The Valve's Opening

Get some high-quality tape and cover the opening of the valve. It'll help you avoid dirt entering the engine inside.

Fourth Step – Check The Valve Closely

Take the valve on your hand and check it thoroughly to identify the reasons that are causing issues. Most probably, you'll get dust particles of carbon. Also, you can get the valve stick on the locking point that's creating a lousy engine idle.

Fifth Step – Clean The Valve Nicely

You should go through this step carefully as it's a vital part of the fixing. Clean the bottom's opening and top of the motor to prevent leaking liquid. We suggest you use a carbon or throttle body cleaner to complete this cleaning task correctly.

Sixth Step – Spraying The Valve Inside

It's time to spray inside a cleaned valve. Also, spray on the dust particles of carbon. Put a jar or bowl if you want to gather all dirt and liquid in a place. If you get the liquid blackish, you must continue cleaning the valve. Get it done when you see the clear liquid coming out from the valve.

Seventh Step – Scrub The Valve Inside

Scrub inside the valve using a pipe cleaner to help clear out any residual dirt and carbon. After cleaning, spray it once again.

Eighth Step – Reversing With The Reinstalling Process

Reverse the installation process by reinstalling the valve. Check your car after reinstalling the valve. That's all.

Frequently Asked Questions – FAQs

How Does IAC Valve Impact Acceleration?

The IAC valve impacts badly on your engine acceleration when it gets defective. A faulty IAC valve can't control the flue and airflow to the engine, so it behaves strangely. Sticking the valve plate demands additional strength to accelerate it. Also, it impacts the braking system.

How To Reset An IAC Valve?

Firstly, park your car in some open space and put it at the "P" point. Now, push the brake pedal down. After that, press and hold down its gas pad for about five seconds. Then, switch the vehicle off, leave it for 10 seconds, and restart it. It should reset the IAC valve.

How Much Does It Cost To Fix An IAC Valve?

A faulty idle air control valve costs between $120 and $500. The prices include parts, labor, and other applicable fees. However, the costs can differ for your vehicle models, locations, and parts brands.

The Bottom Line

Driving with a bad idle air control valve is never recommended, and you learned why you should not do that. When you get any of the abovementioned symptoms, avoid driving your car. Simply take it to the mechanic and fix the issue accordingly.

If you continue driving your car with an IAC valve problem, it'll be a hefty penalty. Even it can damage the engine inside entirely. So, don't do that to save the engine and money from a costlier fine.

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