5 Symptoms of a Bad Idle Air Control Valve
The idle air control valve is responsible for controlling the idle speed of your engine in revolutions per minute (RPM). When it starts to fail, you’ll notice some telltale signs of failure.
We’ll discuss the most common symptoms of a bad idle air control valve, what causes it to fail, and how much it costs to replace this component. Luckily, this part is fairly inexpensive on many vehicles, and you might be able to replace it yourself.
How the idle air control valve works
Engine RPM refers to the number of revolutions per minute. This is commonly referred to as speed. Depending on the vehicle’s current operating conditions, the idle air control valve will increase or decrease the engine’s speed.
For example, if the vehicle is heavily loaded or if the vehicle heats up too quickly, the idle air control valve will adjust the speed by increasing or decreasing the speed. This allows the motor to handle a higher load and in either case allows it to cool down.
The engine control unit is responsible for controlling the idle air control valve. When this central computer receives information about the engine temperature and load, it uses that information to adjust the idle air control valve appropriately. This way, the valve precisely regulates the engine speed based on the information sent by the computer.
If your car’s idle air control valve is faulty, several problems and symptoms will occur. If you don’t replace the valve immediately, your car will not be able to drive. Below are the top 5 symptoms of a bad idle air control valve that you can easily notice:
1) Intermittent Idle Speed
Since the idle air control valve is what controls the engine’s idle speed, a defective valve will definitely throw it off its function. This will cause the idle speed to fluctuate randomly between different speeds instead of staying at a constant speed.
The idle speed may be too high at one moment and too low at another. You can clearly see the idle speed change just by looking at the tachometer on your dashboard.
2) Check engine light
If anything connected to your engine has a slight issue or malfunction, the central computer will turn on the check engine light on your dashboard. This may be due to a faulty idle air control valve.
If the engine control detects an abnormal speed, it will turn on a warning light to warn you. Of course, there are several other possible reasons why the warning light may come on. In either case, you should take your vehicle to a repair shop immediately to have it checked.
3) Rough Idling
A properly functioning idle air control valve will keep your vehicle idling smoothly. But if the valve breaks for any reason, the idle will go from smooth to rough.
If you shut off your vehicle with the engine running, rough idling will cause severe vibrations. Because less air gets into the engine when idling, your car will respond with strong vibrations.
4) Engine Stalls
When the engine stalls due to a failed idle air control valve, your car will not be able to drive at all. As soon as you start your car, the idle air control valve stops working. If this problem occurs when you are not at home, the engine will initially stall every few minutes. You must reach a nearby mechanic in time before the engine stalls completely.
5) Load Causes Stalling (air conditioning)
The engine may stall naturally or it may stall due to increased load on the engine. For example, turning on the heater or air conditioning while the idle air control valve is faulty may cause the engine to stall immediately after.
You may also feel the steering wheel being pulled to the side. To temporarily solve this problem, turn off the heater or air conditioner to reduce the load, then allow the engine to cool for a few minutes.
Cost to Replace an Idle Air Control Valve
If your voltage meter shows a reading outside the normal range, you may need to purchase a new idle air control valve. Unless you are confident in repairing the valve yourself, you will need to pay a mechanic to replace it for you, which means paying for both parts and labor.
The average cost to replace an idle air control valve ranges from $160 to $600. Parts can range from $60 to over $400, and labor can range from $100 to $200. Of course, labor costs will depend heavily on the mechanic’s hourly rate. This job usually takes about an hour, so don’t expect it to cost that much. Some vehicles are more complicated to handle than others, so that’s also a factor.
Causes of IAC Valve Failure
There are several possible causes for idle air control valve failure, and understanding these causes will allow for better (and faster) diagnosis.
1) Carbon Deposits
Over time, carbon deposits can build up on the idle air control valve, restricting the valve’s movement and affecting its ability to regulate airflow. This deposit can be caused by bad or old fuel, short runs, or a fault in the PCV system.
2) Electrical Issues
Faulty wiring or damaged connections around the idle air control valve can cause electrical issues that affect the operation of the idle air control valve.
Though rare, it can also be caused by a faulty engine control unit, but you will find that many other sensors and electrical components are also having issues at the same time. These can prevent the valve from receiving the correct signal or cause the valve to respond incorrectly.
3) Vacuum Leaks
A vacuum leak in the intake system can cause the idle air control valve to work harder than it should, causing premature wear and failure. Vacuum leaks can be caused by damaged or disconnected hoses, bad seals, or cracked intake manifolds.
4) Normal Wear
Like other mechanical parts in your engine, the idle air control valve will wear out over time. As it ages, the valve may become less responsive or not move at all, causing idle speed issues.
5) Contamination
Dirt, debris, and oil contamination can clog the air passages in the idle air control valve, compromising its ability to control airflow. This can be caused by a damaged or clogged air filter, worn piston rings causing oil blow-by, or a failed PCV valve. While a failed idle air control valve is a common cause of idle speed problems, several other engine components can cause similar symptoms. To help you avoid misdiagnosis and unnecessary repair costs, here are some of the most common problems that are similar to a failed idle air control valve:
– Bad throttle position sensor (TPS)
– Bad mass air flow (MAF) sensor
– Vacuum leak
– Bad exhaust gas recirculation (EGR) valve
– Bad oxygen (O2) sensor
– Malfunctioning fuel injector