An engine includes many components, each with a significant function to improve the car’s performance. One such auto component is the idle air control valve (IACV), also known as an IAC valve or Idle Speed Control (ISC) valve.

It is an essential component in modern fuel-injected internal combustion engines. It regulates the engine’s idle speed and maintains stable and consistent idle RPM when the throttle closes, or a car decelerates.

Let’s find out how the idle air control valve functions and the types and symptoms of a bad idle air control valve.

Idle Air Control Valve Working

The primary function of the idle air control valve (IAC) is to regulate the engine’s idle speed by controlling the amount of air that bypasses the throttle plate. When the engine is running at idle, the throttle plate is typically closed, restricting the airflow into the engine. 

However, a certain amount of air is necessary for the engine to continue running smoothly at idle. The IAC comes into play here, allowing the engine control unit (ECU) or car computers to adjust the amount of air entering the engine without altering the throttle position. Besides, here are the signs of bad engine control module.

Here’s how it functions:

• The IAC responds to signals from the ECU, which constantly monitors various engine parameters, such as engine temperature, load, and air intake. 
• These inputs help calculate the required amount of air needed for stable idling.
• The movable pintle or valve opens and closes an auxiliary air passage, allowing air to bypass the closed throttle plate and mix with the fuel in the intake manifold. 
• By adjusting the pintle’s position, the IAC can fine-tune the amount of bypassed air and, consequently, the engine’s idle speed.
• The IAC compensates for the electric load fluctuations by adjusting the idle speed, ensuring the engine remains stable and doesn’t stall. 
• During cold starts, the IAC provides additional air to support the enriched air-fuel mixture until the engine warms up.

Idle Air Control Valve Symptoms

A malfunctioning or failing IAC can lead to various noticeable symptoms in a vehicle. If you experience the issues, such as high or low idle speed, it is a sign of a bad idle air control valve. Here are the ways to check idle air control valve functioning:

Fluctuating Idle Speed 

An unstable or erratic idle speed is the most common symptom of a faulty IAC. The engine may rev up and down unexpectedly at a stop or struggle to maintain a consistent idle speed. If the vehicle’s engine is idling at a speed of more than 1,000 RPMs, it’s probably too high. Also, remember that vacuum leaks can cause a higher idle speed. 

Use an onboard diagnostic (OBD) scanner. If it shows a P0507 code, it can be due to the high RPM generated by the idle air control valve.

Stalling

Besides high idle speed, a failing IAC is a cause of the engine stalling when idle, especially when coming to a stop or during deceleration. The inadequate control of the idle air can lead to a lean air-fuel mixture, causing the engine to shut off.

Rough Idling

The engine may exhibit rough or lumpy idling, with noticeable vibrations and a lack of smoothness. It may feel like the engine struggles to maintain a consistent idle speed. That said, it can be one of the reasons why the car vibrates when idle.

Difficulty Starting

A malfunctioning idle speed control valve can cause a car to take longer while starting the engine, especially when the vehicle is cold. This symptom is more apparent during cold weather conditions. It may also be a reason why a car shakes when starting then dies.

Poor Fuel Efficiency

If the IAC is not functioning correctly, it may allow too much or too little air into the engine, affecting the air-fuel ratio. This rough car engine idling can result in reduced fuel efficiency and increased fuel consumption.

Check Engine Light

A malfunctioning IAC can trigger the vehicle’s onboard diagnostics system and become the reason behind the check engine light turning on the dashboard. Retrieving the trouble codes through an OBD scanner can help pinpoint the IAC as the potential issue. You can find an important car diagnostic code, P0505, for a malfunctioning idle air control valve using an OBD scanner.

Process-1: How to Test IAC Using a Multimeter

You can check the IAC valve’s electrical circuit by performing a resistance test using a multimeter. This test will help determine whether the IAC’s windings are within the specified range. Here’s how to do it:

• Disconnect the electrical connector from the IAC.
• Set your multimeter to the ohms (Ω) setting.
• Touch the multimeter’s probes to the appropriate pins on the IACV’s electrical connector. Refer to the vehicle’s repair manual for the correct pinout and resistance specifications.
• Compare the measured resistance with the manufacturer’s specified range. If the resistance falls outside the recommended range, the IAC valve may be faulty and require replacement.

Process-2: How to Test the Functionality of IAC

To check if the IACV is functioning properly, you can perform a functional test:

• Reconnect the electrical connector to the IAC.
• Start the engine and allow it to warm up to normal operating temperature.
• Disconnect the electrical connector from the IAC with the engine running, 
• Observe the engine’s behaviour. If the idle speed drops or the engine stalls after disconnecting the idle air control valve, it indicates that the IAC is functioning correctly. If there’s no change in idle speed or engine operation, the IAC may be faulty.

These were all the details about the idle air control valve. When buying a used car for sale in the UAE, check the car’s idle speed alongside the road test to determine the issues.

Stay tuned to the dubizzle autos blog to learn more about crucial car parts and components.