What is an Idle Air Control Valve?
The Idle air control valve (IAC valve) regulates the idle speed of your engine. It is controlled by the onboard engine computer system. It regulates the amount of air that circulates around the closed throttle plate.
The idle air control valve contains a solenoid, a coil that operates a valve, which opens and closes to control airflow.
An electrical current that runs through the solenoid determines the quantity of air the valve restricts.
Because the air is electronically controlled the optimal amount can be maintained and responsive to changes in the engine load.
More air circulating = a higher idle speed for starting, deceleration or accessory loading.
Less air circulating = a slower idle speed.
The IAC valve is located on the throttle body. This makes for good accessibility for replacement, however the piece itself is a pricier component of the engine system.
How to tell if your Idle Air Control Valve is going bad
IAC valves are supposed to last the life of your vehicle, however given various circumstances they can require replacement or maintenance.
There are some easy indicators to pay attention to that may signal a faulty IAC valve.
1. Engine Light
The first, and potentially most obvious way is if your engine light comes on.
Modern vehicles will usually experience a check engine light following any IAC failure.
This is signaling to you that something has gone wrong with your engine. When this happens it is important to take your car in right away for assessment, or if you have the proper tools and capabilities check it yourself.
The first step is reading the code of the engine malfunction. A code reader is used to scan the engine computer to isolate the malfunction.
Using an OBD II scanner, you can retrieve the codes. If the codes are between P505 to P509, you have a problem with the idle control system that might be the idle air control (IAC) valve.
2. Rough Idling and Frequent Stalls
If your vehicle is idling inconsistently, or stalling frequently this may be an indicator that your IAC valve needs maintenance.
This is often caused by partial or complete blockages of the valve, from grease, or dirt.
Simply cleaning it, freeing it of debris, may repair a jammed valve.
This symptom can also be caused by a faulty solenoid, which requires replacement.
3. Backfire
If your vehicles backfires this is a sign of a faulty IAC valve. If you take your foot off the gas peddle and your vehicle jerks as it decelerates, and backfires excessive fuel through the tailpipe, this is surely a sign of an IAC valve not operating.
4. Stuck Open IAC Valve
This issue is less common. If your IAC valve gets stuck open, you may notice your vehicle hesitate during acceleration.
What to do if you have identified a faulty IAC Valve
There’s essentially two options for you:
Option One: DIY
DIY for IAC valve is an option in the following circumstances:
1. Your engine light comes on and you have a code reader and …
2. You know how to locate the IAC valve
If you can check the code and isolate the malfunction, a fix may simply mean cleaning out a jammed valve, or in a rare case, shutting a jammed open valve.
A more complicated fix would be replacing the solenoid, or the entire piece.
Code Reading for Different Vehicle Makes
Ford, GM and Chrysler all operate slightly differently when it comes to isolating a malfunction.
WikiHow provides a good resource on how to check your IAC valve for these different vehicle makes.
Option Two: Take it to a shop
If you feel hesitant at all about checking it yourself, then you should take it in. You will save time in the long run by having it addressed by a professional.
Save piece of mind if you have little vehicle knowledge, and take it in.
Do you have any other questions about IAC valves?
Let us know and we will try our best to answer.