Bad Idle Control Valve: What Are the Causes and Solutions?

A bad idle control valve can damage your engine if you don’t take appropriate steps to rectify the situation. Thus, you need to be conversant with the symptoms so that you identify them once they rear their heads.

Bad Idle Control Valve

This will save your engine and money when you take early measures because a stitch in time saves nine. In the paragraphs below, we’ll highlight some of the symptoms and take you through how you can repair them.

What Causes a Bad Idle Control Valve?

A bad idle control valve has three common causes: a dirty engine, a clogged idle air control valve, and a failed solenoid inside the idle air-control valve. These can hamper your vehicle’s acceleration, cause it to stall, make it backfire, or even damage the engine.

– An Excessively Dirty Car Engine Bay

An extremely dirty engine, especially one with an overly dirty engine oil, can carry contaminants as it flows through the engine. These dirty contaminants can build up over time and cause the failure of the idle control valve which, in turn, can hurt the engine.

Thus, you need to change the engine oil on schedule to keep the engine clean at all times. You should also carry out periodic cleaning of the engine to get rid of all dirt and grime that may hamper the engine’s performance.

– A Congested Idle Air Control Device

The idle air control device allows air, which may contain some debris, to pass through it into the engine. Over time, this debris can clog the valve or damage parts of it and cause malfunctioning of the device.

What Causes a Bad Idle Control Valve

Usually, this isn’t a huge problem as simply cleaning the idle control device will get it functioning properly again. However, if its parts are damaged due to clogging, then you may have to replace the entire device.

– A Failed Solenoid Idle Air Control Valve

A solenoid in the idle air control valve helps determine the quantity of air that should enter the engine. The solenoid runs on electrical current which allows it to function properly. Thus, if the solenoid fails, the idle air control valve would malfunction as it can’t dictate the right amount of air to be placed into the engine. The only way to manage this situation is to have the solenoid replaced and the device cleaned.

What Are the Solutions to a Bad Idle Control Valve?

The solutions to a bad idle control valve is either of two ways: clean the device or replace it. The easiest and cheapest of the two is cleaning it, which you can do or get a professional to do for you. However, you can purchase the entire device as well.

But first, you need to determine whether the IAC valve is faulty because rough idling has several causes. To do this, you’ll have to run a quick test called the idle RPM procedure, which involves measuring the idle RPM when the IAC valve is in the car and when it is removed.

First, turn on your vehicle and study the tachometer while waiting for the RPM to stabilize, which may take a while. Once the RPM is stable, record the value on a piece of paper or your phone and proceed to the next step. Now turn off the engine and remove the IAC valve, which is found on the throttle body. Once the valve is out, turn on the car again and allow the RPM to become stable.

Record the value of the RPM on the same sheet of paper and compare the two numbers. If the numbers are different, then it means that the IAC valve is working fine. However, if the numbers are the same, then the valve may be faulty and you can confidently move on to cleaning or replacing it.

– Cleaning the Idle Air Control Valve

To do a comprehensive job, you’ll need the right tools, which are a socket wrench, wrench, screwdriver, and a can of throttle body air and air intake cleaner. Make sure you don protective clothing including a pair of goggles, gloves and a nose mask.

Fixing Bad Idle Control Valve

Once your tools are set, locate the idle auxiliary air valve, which is found either on the side of the throttle body or on the intake manifold. When you find it, remove the vacuum hoses connected to it, including the auxiliary air valve connector. The next step is to loosen all the bolts (usually three or four) that are holding the IAC valve in place and remove the device.

First, use a toothbrush to remove all the dirt, grime, and/or debris that may have accumulated on the device. Spray the whole the IAC valve with the cleaner, making sure that it enters every corner of the gadget. Allow five minutes for the cleaner to do its work then use the toothbrush to get rid of all carbon deposits and your device will be good as new.

Now, install the gadget and ensure that the bolts and vacuum hoses you removed earlier are properly fixed. Restart the car engine to check whether the symptoms have disappeared. If they persist, then you should consider control valve replacement. Replacing the valve is quite simple, especially if you know what you’re doing, which we’ll demonstrate in the next few paragraphs.

– Replacing an Idle Control Valve

Replacing an IAC valve usually takes around 30 minutes and the replacement cost is between $100 to $300 depending on the vehicle. The tools you’ll need are similar to those used in cleaning the device, including a socket wrench, wrench and screwdriver. Always wear protective clothing when dealing with faulty issues in your car. Now that everything is set, consult your car’s manual to help you find the IAC valve.

Just as stated earlier, unplug all the hoses connected to the valve and unscrew the bolts used to fix the device. Take out the old device and replace it with the new one. Screw it in place and then reconnect the vacuum hoses to it and you’re done. Test the idle speed of the car and if it is either too high or too low, you’ll need to conduct a reset to align the new device with the ECU.

To do this, disconnect the negative terminal of the battery and allow it to lie for about an hour. Then reconnect the negative terminal and take the car for a 15-minute test drive. This enables the ECU to “familiarize” itself with the new device. However, note that this method is universal and may or may not work on your vehicle, thus contact your car’s manual for assistance.

– Changing the Engine Oil Will Help

Since excessively dirty engine oil can cause a faulty IAC valve, replacing it frequently might prevent it from happening. First, put on protective clothing like gloves, goggles and aprons to ensure your body doesn’t come into contact with the oil. Next is to jack up your car so that you can get access to its underside. Now, place a drain pan or a large container directly underneath the drain plug and remove it to allow the old oil to flow out into the container.

Once the dirty oil is completely drained, look for the oil filter which will be in a cylindrical component and screwed onto the underside of the engine. Remove the cylindrical component and wait for the oil inside it to flow out, then take out the filter and the old gasket. Replace the drain plug and the filter. Now, pour the new oil into the engine to the desired level using a funnel.

– Resetting the Idle Air Control Valve of Your Engine

You can also reset the IAC valve of your engine to ensure that it works properly. However, note that this procedure is just a temporary fix until you get a professional to replace the valve. Resetting the IAC valve involves turning the car on and then putting the gear into “park.” Now, press the brake down and then press down the accelerator pedal slowly until the pedal stops.

The next step is to steadily take off your legs from both pedals until they are fully released and then allow the car to stay on for 5 seconds. Once the seconds have elapsed, turn off the vehicle and wait for another 10 seconds before turning it back on. This should reset the IAC valve, therefore perform a quick check to see if it is working properly. If it doesn’t work, know that it is just a stop-gap measure, so look for a mechanic to help you out.

Take note that just unplugging the air control valve may temporarily stop the symptoms of IAC valve failure, but won’t make it go away. However, you’ll need to learn how to bypass idle air control valve or you may end up worsening the process and damaging the engine.

Frequently Asked Questions

– Can a Bad Idle Air Control Valve Cause Misfire in the Engine?

No, a bad idle air control valve can’t misfire in the engine unless there are vacuum leaks around the intake manifold to the auxiliary air valve seal. Misfire only happens when the fuel injector doesn’t provide enough fuel or there’s an insufficient spark to combust the air/fuel mixture.

– What Are the Common Bad Idle Control Valve Symptoms?

The common symptoms of a bad idle air control valve are engine stalling, a surge in engine speed, illumination of check engine light, and idle speed fluctuation. Others include engine backfire, delay in acceleration, and an engine that is difficult to start.

Bad Idle Control Valve Detailed

Can an Idle Control Valve Issue Cause IDM Failure in a 7.3 PowerStroke Engine?

A potential concern in a 7.3 PowerStroke engine is whether an idle control valve (ICV) issue can lead to powerstroke IDM failure symptoms. While the two are separate components, a malfunctioning ICV can cause irregular idle speed, leading to increased stress on the IDM. However, further diagnostic testing is necessary to determine the exact cause of IDM failure in a PowerStroke engine.

How Does a Bad Idle Control Valve Affect the Rough Idle When AC Is On?

A bad idle control valve plays a significant role in causing a rough idle with AC on. When the AC is turned on, the compressor puts extra load on the engine. If the idle control valve fails to regulate the engine idle speed properly, it may result in an inconsistent and rough idle, adversely affecting the overall performance of the vehicle.


A faulty or clogged idle control valve can damage your engine, therefore, once you notice it is failing take immediate steps to rectify the situation.

Here is a recap of other important points made in this article:

  • Factors that cause this problem include excessively dirty engine oil and a damaged solenoid.
  • To rectify these problems, clean the IAC valve with a dedicated cleaning agent and if it doesn’t work, replace the entire device.
  • You can also change the engine oil, especially if the car has just started showing signs of a bad control valve.
  • Replacing the device can be done in a few easy steps, however, if you have to reset it, then consult the car’s manual.

You can also try the universal method of resetting by disengaging the battery’s negative terminal for about an hour then taking the car for a 15-minute drive. This should re-align the car’s engine with the new IAC valve.

5/5 - (15 votes)
Ran When Parked