How to Test an IAC Valve With a Multimeter?

IAC stands for idle air control, and it is responsible for controlling the flow of air into the engine and how much fuel your vehicle will burn. A faulty IAC can lead to poor gas mileage, increased emissions, and other problems. 

Fortunately, checking if your IAC is working correctly requires any high-tech equipment or even special tools. You’ll need a multimeter which you might already have lying around in your garage!

When your vehicle is not running right, and you take it to the mechanic, they will find a problem with your IAC valve. You may be asking yourself, “What exactly is an iac valve?”. 

The acronym stands for Idle Air Control Valve. It’s a device that regulates how much air goes into the engine at idle speeds.

The most common way to test an IAC valve is with a multimeter. This blog post will show you step by step how to do just that!

Signs Of A Bad Or Failing Idle Air Control Valve (IAC)

When a faulty idle air control valve (IAC) fails, it can cause all sorts of issues; and, in some cases, may even render the car undrivable. 

A bad or failing Idle Air Control Valve (IAC) usually produces a few symptoms that alert drivers to potential issues:

Irregular Idle Speed

One of the most common symptoms associated with a problematic idle air control valve (IAC) is irregular idle speed. 

Because it’s tasked with regulating and maintaining engine idling, if your IAC system has any issues, you may experience an unusually high or low rate that climbs up then falls.

Check Engine Light Illuminated

If you see your Check Engine Light come on while driving, it might be due to an issue with the idle air control valve. The trouble is sometimes that diagnosing what’s wrong can take a lot of time and money!

If you’ve noticed some engine roughness or hesitation in recent weeks, ask us about this possible cause for concern so we can help diagnose any potential issues before they become expensive problems.

Check Engine Light

A wide variety of issues can also set off the Check Engine Light, so it’s highly recommended to have your car scanned for trouble codes.

Rough Engine Idle

A standard healthy idle air control valve (IAC) will provide smooth idling in your vehicle. But if the IAC goes bad for any reason, the engine’s running becomes rough and shakes from intense vibrations when stopped with its engine on. 

A rougher idle state is due to less airflow entering due to an unstable condition that could be caused by corroded electrical contacts or fluid leaks that cause it not to function correctly.

Engine Stalling

The idle air control valve (IAC) is the heart of your vehicle’s engine. The IAC regulates airflow to keep an idling, healthy engine running smoothly and without stalling or other issues. 

When it malfunctions, you may experience a variety of symptoms such as stalls while operating or when starting from scratch; lackluster performance on hills and inclines; poor fuel economy with longer distances between fill-ups than usual–or no improvement at all!–and more severe problems like hard shifting and rough braking because there will be less power available for those functions if the car needs more momentum.

Stalling Under Load

Sometimes the engine will stall on its own, but other times you can cause it to restart by the increasing load. 

For example, turning up your heat or air conditioner when a bad idle control valve (IAC) is present leads to an immediate stall of the engine and might also drag one side of the steering wheel too – with that in mind, be sure not to turn off anything while driving!

Checking IAC Valve Resistance Specification Using a Multimeter

  • Step 1: To access the IAC valve on your vehicle, consult with the service manual.
  • Step 2: Disconnect the IAC valve. Locate the connector for your vehicle’s IAC, and unplug it from there.
  • Step 3: Use the procedure detailed in your vehicle service manual to remove the IAC valve.
  • Step 4: Inspect the IAC valve. Inspect the valve and mounting location for carbon build-up, rust, or dirt. Inspect the IAC Valve Pintle and Mounting Location For Damage before condemning it if there are no obvious signs of wear on either end.
  • Step 5: When you test the IAC valve for a reading, make sure that your multimeter is set to Ohms and follow these instructions. The first step in trying an IAC valve with resistance readings at 5-10 ohm should be checking out its connector terminals. If it falls within specification, then the fault may lie elsewhere, but if not, replace it with a new one as soon as possible!

It’s essential to keep your idle air control valve in perfect working order as it can directly affect the engine idling speed. 

Bypasses allow fresh coolant and air into the engine when idle, so replacing any damaged seals is critical, or you could end up with leaks!

You can find the idle air control valve on most vehicles, and it does an essential job of managing engine speed. It eliminates air by bypassing your throttle body, which lets you enjoy a smoother ride when you’re idling.

As you can imagine, a bad or failing idle air control valve will cause the engine to act erratically by affecting the idle speed and frequently causing it to cut out entirely. 

If this is happening in your vehicle, there are some simple ways that you may be able to troubleshoot this issue at home. 

An excellent place to start would be checking if anything has changed with any of the sensors on your car recently – such as a new battery installed or hoses replaced, which could have affected how well they work together with other components like an IAC Valve (Idle Air Control Valves). 

You should also make sure that all fluids levels are topped off, so nothing comes up short while trying to diagnose potential issues here, either. Other than these

About Blake Sutton

Blake has worked as an electrician for over 10 years, receiving his Journeyman Electrician license in 1998. Looking to take his professional electrical career further, in 2008 he received his Bachelor of Science in Electrical Engineering (BSEE) from the University of Texas in Austin. Blake now works full time as an electrical engineer, specializing in power systems.