idle air control valve

Everything you need to know about idle air control valve

The idle air control valve, commonly referred to as the “idle speed control valve,” manages how quickly your engine idles. The computer in the engine is in charge of this. Your car may occasionally stall or idle abnormally due to faulty parts. Before attempting to repair your idle control valve, be sure it is operating properly. Your automobile may be trying to notify you there’s a problem if your idle starts to nervously quarrel.idle air control valve

Idle difficulties can frequently, but not always, be caused by a broken or clogged idle air control valve, a little component next to the throttle body that does precisely what its name suggests. Fortunately, it’s usually a reasonably simple item to access, maintain, and replace, which is great news for garage lubbers everywhere.

Well, in this article, we’ll be discussing idle air control valves. Nonetheless, the answer to the following questions will be covered:

  • What is an idle air control valve?
  • How does the idle air control valve work?
  • Where is this valve located?
  • What are the bad or failing symptoms of an idle air control valve?
  • How to check the valve?
  • Can you drive with a bad idle air control valve?
  • How much does an idle air control valve replacement cost?

Ok, let’s dive in!


What is an idle air control valve?

The idle air control valve is one of the few auto parts with a name that fits it so perfectly. It is a valve or other mechanism that opens and closes to allow air or fluid passage (air in this instance) into the engine. The air required to keep the idling speed constant is managed by the idle air control valve. In essence, it serves as a throttle body plate bypass.

The idle control valve in your car analyzes all the variations and modifies the idle speed of your engine to maintain smooth operation. Although it may not be the most appealing component around, its absence might cause your engine to stall and a number of performance problems.

Although you’ve become accustomed to expecting your engine to keep a constant RPM regardless of what you’re doing, your engine couldn’t do this successfully without an idle control valve. That’s because a wide range of circumstances might have an impact on the idle speed of your engine.

Your idle speed can vary depending on a variety of factors, including your present altitude and the number of accessories your engine is running. An idle air control valve may experience either clogging or failure, two common problems that both call for your skilled touch with a wrench.

It is possible for pollutants to reach the valve chamber because of the airflow through the idle air control valve. These impurities or contaminants may clog, jam, or harm the internal workings of the part, leading to a malfunctioning valve. Additionally, the idle air control valve won’t function properly and the car probably won’t be able to start if the solenoid inside stops working, the valve stops receiving an electrical signal, or the seals deteriorate.

How does the idle air control valve work?

The working of idle air control valves confuses a lot of individuals. A closed throttle plate is physically bypassed by air via an idle air control valve, allowing the engine to receive air when idling. It is also known as an air bypass valve since it does so. The idle speed adjustment screw was used in the days of carburetors to control idle speed.

In reality, many carburetors included two screws for adjusting idle speed—one for hot idle and the other for cold idle. The amount the throttle plate remained open affected how much air could flow into the engine. Turning the screw inward stopped the throttle plate from fully shutting.

Remember that a carburetor requires air to pass through the throttle plate and into a venturi in order to create the vacuum necessary to suction gas from the carburetor bowl. The throttle would go to the “cold” position when the engine was cold, and the cold idle screw would keep the throttle plate open far longer than it would at hot idle.

This made it possible for more air to enter, more suction to develop, and more gas to enter the cold engine. The choke would not engage the cold idle cam on a hot restart, and the throttle plate would only open slightly to let a tiny quantity of air in. Therefore, you would only obtain enough gas to keep the engine going while it was warm. That is not how fuel-injected automobiles operate.

The throttle body doesn’t have a venturi, to start. Its sole function is to control the amount of air that enters the engine. The powertrain control module (PCM) or engine control module (ECM) checks the engine coolant temperature, the outside air temperature, and the barometric pressure (on some engines) during start-up before calculating the amount of gas and air needed to start the engine.

When starting a fuel-injected engine, car manufacturers advise against pushing the pedal. This indicates that the throttle plate is fully closed. The engine gets air in what way? by way of the idle air valve. Because it BYPASSES air around the throttle plate to give combustion air at idle, the true name for this component is the idle air bypass valve.

Where is this valve located?

The throttle body is normally where you’ll find the idle air control valve. On cutting-edge engines, the idle control valve is primarily integrated into the throttle body. On older engines, it was an exterior unit positioned close to the air intake.

In spite of engine and climatic conditions, it can then effortlessly regulate the airflow to your engine to maintain a constant idle. The good news is that since it’s normally located close to the top of your engine, replacing it yourself is usually not too difficult. The idle control valve is one of the simpler parts to access.

What are the bad or failing symptoms of an idle air control valve?

Your car may alert you to a problem with the idle air control valve in a number of ways. Be aware, though, that these signs are fairly generic, making them less reliable as diagnoses. The idle issues may continue even after you check, clean, or replace your valve because of issues with the engine as a whole. The following are the most common symptoms you’ll likely notice if your idle air control valve is bad or failing:

  • Starting Issues: An engine may not start or may start slowly if it isn’t getting enough air. This can point to a problem with the idle air control valve.
  • The car Starts, Then Dies: 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.
  • Backfiring: The air-to-fuel ratio will be off if the engine doesn’t have enough air, and some gasoline may remain after the spark. Following that, when the fuel moves through the system, a backfire can result.
  • Poor or rough idle: An irregular source of air entering the engine will produce a glugging, hesitating, revving, and dying sound. You’ll be aware of the situation.

How to check the valve?

In this section, I will guide you through the process of checking the idle air control valve. Specifically, we will be focusing on three key things:

  • Finding Problems with an Idle Control Valve
  • Verifying the Idle Control Valve’s Operational Status
  • Examining Problems with Specific Makes

Finding Problems with an Idle Control Valve

Pay attention to a high engine idle

A high idle might be a common sign of a broken idle control valve. Start the engine, then observe the dashboard’s tachometer. The majority of car engines will idle at or below 1000 RPMs. Compare the present RPMs to your engine’s regular idle if you are familiar with it. The vehicle’s engine is definitely running too high if it is idling at a rate much above 1,000 RPMs. A high idle might also result from vacuum leakage.

Pay close attention to low idle or stalling

A malfunctioning idle control valve can also be the cause of low idle and even irregular stalling in addition to high idle problems. Once more, start the engine and compare how it is operating at a halt with how it is operating normally. Your idle control valve may be malfunctioning if the idle is low and erratic. Vacuum leaks may potentially be the cause of low idles.

If the check engine light comes on, take note of it

Your car’s check engine light will come on if the Engine Control Unit (ECU) detects a problem with the way the engine is operating. Look at your dashboard; if the check engine light is on and you’re experiencing idle problems, it’s possible that the idle control valve isn’t working properly. The check engine light resembles a crude engine drawing. Idle problems and a check engine light may be signs of a broken idle control valve.

Watch for indications of a vacuum leak

Try to identify any possible vacuum leaks that may be the source of your engine’s poor idling. Visually check your engine bay’s vacuum lines for signs of damage like cracks or excessive wear. To test the strength and consistency of the vacuum, remove a vacuum line and attach it to a vacuum gauge. To check for bubbling at the source of a leak, you can also try spraying a soap-and-water solution on the lines.

Verifying the Idle Control Valve’s Operational Status

To check error codes, use a code scanner

You’ll need an OBD I scanner if the year of manufacture for your car is before 1996. After-1996 vehicles require an OBD II scanner. Turn on the code scanner by plugging it into the connector under the dashboard. Using the scanner after connecting will allow you to view the error codes that are causing the check engine light to illuminate. Some code scanners will display the fault code’s English description on the readout. If your code scanner does not, you must seek up the code the scanner displays in order to determine its meaning.

Watch the idle RPMs after starting the engine

Start the engine by inserting the key into the ignition. Use a pen and paper to note the RPMs that your engine settles and idles at after waiting a minute for the engine’s idle to level off. For the engine to slow down to its regular idle speed, you might need to let it run for a few minutes. As you continue the test, keep the piece of paper you used to record the RPMs nearby so you can compare it to the engine idle.

Turn off the engine and unplug the idle control motor

As soon as you have noted the idle RPMs, turn off the engine again and take the key out of the ignition. Find the Idle Control Motor by lifting the hood. Disconnect it once you’ve found it. Depending on the application, there may be a different way to disconnect your idle control motor; for more detailed instructions, consult the service handbook for your vehicle. Typically, you can turn off the idle control motor by unplugging the cable clip that connects to it.

Start the engine again

Get back inside the car and restart the engine with the idle control motor unplugged. Even with the idle control motor disconnected, the engine should still start and operate normally. To prevent the detached wiring from being entangled with any moving parts, be sure to tuck it away in the engine compartment.

Keep an eye out for a change in idling speed

Take note of any variation in the idle RPMs from the idle you previously saw after letting the engine run for a minute to settle into a steady idle. Your idle control motor probably hasn’t been working if the idling hasn’t moved at all. Disconnecting the idle control motor should have altered the engine’s idle if it were in operation. This test indicates that there is a problem with the idle control motor but does not identify what it might be.

Reconnect the Idle Control Motor after turning off the engine

If you noticed a difference in the engine’s idle RPMs between starting it with the idle control motor connected and starting it without, reattach it to verify your theory. When the idle control motor is reconnected, the idle should return to its previous state. To compare it to your initial reading, refer back to the note you made on idle RPMs.

Examining Problems with Specific Makes

Check the solenoid resistance in a Ford

Identify the two electrical pins on the solenoid and the idle control motor in your Ford. Measure the resistance between the two by connecting an Ohm meter to them. Fords are made to function with solenoid resistance in the range of 7.0 to 13.0 ohms. Replacement of the idle control motor is required if the resistance is outside of that range.

For a Chrysler, raise the idle speed using a bidirectional scan tool

Use the same OBD port that you would use to plug in a code scanner to connect a bidirectional scan tool. To boost the engine’s idle, use the scan tool’s command. If there is a problem with the idle control motor or its circuit that prevents the signal from modifying the idle, the engine idle will not increase. A bidirectional scan instrument is available at your neighborhood car parts store. Before doing this test, make sure the wiring harness is securely attached to the idle control motor.

To inspect the wiring on a GM idle control motor, use a test light

Use a test light, and attach the negative lead to the car’s body. In each of the four circuits on the GM idle control motor, insert the test light. While the engine is running, each circuit should cause the test light to flash or change from bright to dim. If the test light does not blink for each circuit, the idle control motor is not the source of the problem; rather, it is the ECU. It is necessary to replace the idle control motor if the test light flashes correctly.

Can you drive with a bad idle air control valve?

Typically, a damaged idle air control valve will result in a number of warning indications that will let you know as soon as there is a problem with the engine. Even though it’s uncommon, a damaged valve might occasionally make an automobile impossible to drive. Though technically possible, it is not advised to drive with a faulty idle air control valve. It frequently results in engine stalling, which endangers the safety of the moving vehicle. Furthermore, keep in mind that if a defective valve is the cause of the check engine light being on, you won’t pass a state emissions test.

How much does an idle air control valve replacement cost?

The cost to replace an idle control valve ranges from $100 to $500 on average. Remember that these rates can change depending on the vehicle you drive and the shop you use for repairs. Although this could appear to be a significant cost variance, practically all of it is due to differences in part costs. The price of an aftermarket idle control valve ranges from $50 to $400, and if you want an OEM replacement part, you might have to pay even more.

The labor costs, on the other hand, are often between $50 and $100. This implies, however, that if you want to try to save some money by completing the task yourself, you won’t save all that much compared to the entire repair cost. The good news is that some parts are simpler to replace than others.

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Watch the video below to learn more


What does idle air control valve do?

On the throttle body of fuel-injected engines is the idle air control (IAC) valve. To ensure smooth idling, this valve collaborates with the vehicle’s ECU to electrically control airflow to the engine.

What happens if I unplug the idle air control valve?

Therefore, removing the idle air control valve may have a detrimental effect on how well the engine runs. It might even harm the engine permanently in some circumstances. As a result, unless absolutely required, it is typically not advised to remove the idle air control valve.

What causes idle air control valve?

Idle Air Control Valve Failure: What Leads to It? Idle air control valves are made to last the lifespan of the vehicle, however, neglecting maintenance can result in an early failure. As you may anticipate, carbon and grime build-up are the most typical causes of failure.

Can a car run without an idle air control valve?

If everything else is in order, an engine can run even with the IAC unplugged. The IAC may need to be disconnected, the base idle set using the throttle plate screw, and then the IAC reconnected if a base idle speed change is required.

Can I clean idle air control valve?

The screws holding the idle air control valve to the throttle body must be unscrewed. To completely remove the valve, cut any cables coming from it. Soak the valve in gasoline to clean it. To make sure the gasoline gets inside the valve while it is soaking, move the flap.

What sensors control the idle air control valve?

The engine management system uses an input signal from the ECU to operate the IAC valve. The duration and frequency of the input signal define how long and how far the IAC valve opens, which in turn influences how much air is permitted to bypass the throttle plate.

What controls idle speed?

An electronically controlled throttle bypass valve is used to regulate idle speed. This valve allows air to flow around the throttle plate and has the same effect as if the throttle had been slightly opened, allowing enough M. a to flow to keep the engine running.

Does an idle air control valve affect performance?

Many different components and systems make up your car, all working together to keep it 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. When this component breaks down, it may result in uncomfortable sensations in your car and major performance problems.

And that’s it for this article, in which we discussed close to if not everything about the idle air control valve. Nevertheless, the answers to the following questions have been discussed:

  • What is an idle air control valve?
  • How does the idle air control valve work?
  • Where is this valve located?
  • What are the bad or failing symptoms of an idle air control valve?
  • How to check the valve?
  • Can you drive with a bad idle air control valve?
  • How much does an idle air control valve replacement cost?

Hope you learn a lot from the reading. If you do, kindly share it with others. Thank you for your time; see you soon!