Idling is when the car’s engine is running; however, your vehicle remains in the same spot. When idling, the RPM changes. A component called idle air control manages an engine idle speed. This is a very important part of an engine because, without it, RPM can increase or decrease according to the operation of your car. It’s also important to learn about the different bad idle air control (IAC) valve symptoms, especially at an early time, to prevent problems with your vehicle.
Bad Idle Air Control Valve Symptoms
Before we go ahead and identify each bad IAC valve symptom, let’s first understand the main function of this component.
This valve is found along the throttle body and is managed by the control unit of your car’s engine. From the information that this valve receives (temperature and engine load), it will increase or decrease the car’s idle speed. Driving with a bad IAC is dangerous, and therefore, you should have your car checked as early as you spot any of the following symptoms.
1. Changing idle speeds
The IAC valve manages the engine idle speeds, and thus, having a broken valve can dramatically affect idle speeds. You will notice that your idle speeds can randomly increase or decrease to different speeds rather than remain in one speed. Check your tachometer on your car’s dashboard, and you’ll see high readings and then low readings after a few seconds.
2. Flashing check engine light
The check engine light could be due to any problems with the car’s engine, but when it flashes along with noticeable changes in idle speeds, then there could be problems with your IAC valve.
The engine check light activates if the RPM at idle seems peculiar to the engine. And because there are a lot of reasons why this light may activate, it’s wise to have your car checked by a certified technician right away.
3. Intense idling
The troublesome IAC valve can cause less air to enter into the engine while the car is in idle. When this happens, the car will start to shake intensely, and the vibrations happen when your car is stopped while your engine is still running. It’s hard to overlook this symptom because you will feel as if the entire body of your car is vibrating. Take your car to an auto shop as early as you notice this very peculiar symptom.
4. Engine stops
Your car’s engine will stall, and usually, it will happen several times before you can drive it. As soon as you experience engine stalling, drive your car to a nearby auto repair shop to have it checked. If you overlook this, it won’t be long when you can’t even start your engine.
5. The excess load will make the engine stall
Even additional load to the engine like turning on your air conditioning or heater can stall it. You may also find the steering wheel being dragged to the right or left. If this happens, turn off the air conditioner or the heater. This is only a temporary fix. You must take your car to an auto shop ASAP.
Consider checking other systems that take power from the engine. Try switching lights, heating, and cooling systems to zero in on IAC problems.
6. Diagnostic trouble codes in the PCM
A reliable mechanic uses special electronic diagnostic equipment to check your car’s engine. If there’s something wrong with your car’s IAC valve, the PCM or Powertrain Control Module will read error codes P0506 or P0507.
Error P0506 means that the RPM of the idle control system is low or lower than expected. An error code P0505 OBD-II means an IAC system malfunction or idle air control malfunction. Error code P0507 is the opposite. The ECM detects that the idling time is higher than expected. Take note that the standard engine idle time is from 600 to 800 rpm and is based on the vehicle’s model.
The idle IAC symptoms in a ford Ford, Honda Civic IAC symptoms, and all vehicle make and models are the same. What's important is you have your car checked the first time you notice any of these symptoms
How much to replace an idle air control valve? The IAC valve replacement cost depends on the cost of the component (the idle air control) and labor costs. The control valve costs around $45 for basic car models and may be as expensive as $400 for updated and high-value car models. Labor costs may be from $50 to $70. Most mechanics charge by the hour, but don't worry since replacing the IAC valve will only take less than an hour to do.
Take note that labor costs may become higher if intensive car diagnostics are done. For instance, you’re still unsure if a bad IAC is causing your check engine light to flicker or to light up without warning, then the mechanic may perform tests on other engine components to rule out the source. Other updated car mechanics use a special electronic diagnostic tool to determine car engine problems, and this is where error codes like the P0506 or the P0507 are identified.
You can avoid idling problems by taking your car to a mechanic at least once or twice a year. A mechanic can run full diagnostics and maintain your car even before the first bad IAC symptom arises. You may also find products that can improve the performance by cleaning the throttle component and the IAC, but be very careful following these DIY videos and using products. You need a good working knowledge of the location of the IAC and how to disable your engine to clean this particular component.
It’s best to have a professional help you with dealing with engine problems. It's your job as the car owner and driver to understand these troublesome IAC symptoms and to be keen on detecting bad idle air control valve symptoms before you end up with a stalled car.
James is a certified auto technician specializing in commercial vehicles. With 30 years of experience under his belt, James has encountered almost every type of automotive issue there is! Besides his day job at the repair shop, he is also an amateur race car driver.