A car with a faulty idle air control valve can be a threat to the owner because of the effects of the malfunction of the component. Several idle air control valve symptoms militate against the safety of a vehicle and its owner.
It would be best to look out for these symptoms and fix the issue immediately to avoid an imminent accident. Also, fixing faulty vehicle parts on time will necessarily help to curb spending more money to replace them when they fail completely.
Introduction to the Idle Air Control Valve
The IAC valve regulates idle – the rotational speed of the engine when the vehicle is running but not moving – by controlling the air that enters the engine while idling.
It does so in response to the demands of various components, such as the power steering pump or the AC compressor, to ensure the engine doesn’t stall and response to your throttle is smooth.
The IAC valve works with your vehicle’s main engine computer, receiving a signal that controls its position. It’s typically located on or near the throttle body and consists of a solenoid-operated plug that opens and closes to control air flow.
A functioning IAC valve ensures that your engine maintains a consistent idle speed. This is critical for smooth acceleration and is a key part of your vehicle’s emissions control system.
The IAC valve also adjusts the engine’s air-fuel ratio to compensate for different operating conditions, meaning it plays a part in both performance and efficiency. When your IAC valve starts to fail, the results are quickly evident.
How Does An Idle Control Valve Work?
Please be noted that each manufacturer designs a different type of IAC valve but they share the same operating principles. How the IAC work are divided into 4 steps.
Step 1
The IAC valve in most cases is installed on the throttle bore to adjust the air intake into the engine at idle mode. The power control module got feedback data from sensors to command the air passage to open or close.
Remember that the valve will not be used and has nothing to do with the engine at speed over idle mode. The idle speed of the engine is designed to be constant and fixed.
Step 2
When airflow blows through the IAC valve, the volume of air will be adjusted by the opened/closed ports inside the valve.
These ports are sealed by a gasket to prevent air leaks. Some valves have a part using coolant to cool down the air at 85 Celsius degrees to improve the air intake volume.
Step 3
When the IAC valve is running, the airflow bypasses the valve through the passage in front of the butterfly. Then it comes into the throttle bore by the passage next to that, at this time the butterfly is closing completely.
Step 4
Due to the regular huge volume of air passing through the valve, a condition called coking augments and hampers the operation of the valve. Therefore, cleaning the valve periodically is a must to avoid idle air control valve symptoms.
Idle Air Control Valve Symptoms
When the IAC valve fails, you’ll likely notice a variety of issues that signal trouble. Here’s what to look out for:
- Irregular or fluctuating idle speed – A clear sign of an IAC valve problem is when your engine’s idle speed fluctuates, sometimes quite dramatically. You might notice the tachometer bouncing around, and the engine may sound like it’s sputtering.
- Hard engine starts – A faulty IAC valve can lead to difficulty in starting your car, especially in cold conditions. Erratic idling can prevent the engine from finding a stable speed for successful ignition.
- Engine stalling – If your vehicle stalls when you come to a stop or when idling, it can be a result of a bad IAC valve. The valve may be failing to regulate the idle air properly, which means the engine may not have enough air to continue running smoothly.
- Poor performance – A vehicle experiencing a loss of power or misfiring when accelerating may have an IAC valve issue. This symptom is often more noticeable when you hit the gas to increase speed or climb hills.
- Check Engine light on – The IAC valve’s performance is continuously monitored by the engine control module. When the module detects an issue, it will trigger the Check Engine light to warn you of a potential problem.
What Causes Idle Air Control Valve Failures?
- Contamination and Clogging: Contaminants and carbon deposits can accumulate within the IAC Valve chamber due to the continuous flow of air. These deposits can obstruct or completely block the valve’s passageways, leading to internal damage, jamming, or clogging. This can result in a malfunctioning valve, often caused by low-quality fuel or inadequate maintenance.
- Electrical Problems: A poor electrical connection, especially in older vehicles, can contribute to IAC Valve malfunctions. Loose or corroded connectors, as well as short circuits, can also affect the valve’s proper operation.
- Worn or Damaged Internal Components: Over time, the internal components of the IAC Valve can wear out or become damaged due to normal use or excessive heat. This can lead to reduced valve performance or complete failure.
Where Is The Idle Control Valve?
Most vehicles have their idle air control valve connected to the body of the throttle, and it sits beside the car’s intake manifold. The component is often located on top at the midpoint of the engine.
However, this location is not the same for all vehicles. So, endeavor to check your car’s manufacturer’s manual to ascertain where the IAC valve is located.
It is also possible to trace the location of the idle air control valve by tracing the hose of the air cleaner through to the motor’s top. However, while doing this, ensure to disengage the car’s battery to avoid a shock.
If finding the idle air control valve seems stressful, you can consult a professional auto mechanic to do the job. It will only cost a few bucks. You can choose to check out the process of locating the idle air control valve via a video online.
How To Troubleshoot And Fix Idle Air Control Valve?
Driving with a bad idle air control valve is quite risky. Suppose you notice any of the symptoms of a defective idle air control valve slightly. In that case, you can carry out a swift fix to troubleshoot the fault before you eventually replace the component.
#1. Test the idle or transmission air control valve.
Firstly, you could perform a test on your car’s IAC valve when you notice any sign of a perceived faulty. The idle air control valve test can be done as follows.
- Turn OFF the air conditioner and radio.
- Listen to the car’s engine sound/noise.
- Ensure to note the car’s RPMs, which are expected to be a minimum of 600 and a maximum of 1,000.
It is important to note that a low RPM signifies a fault in the idle air control valve or a leaking vacuum in the car. You may need to find out how to adjust idle air control valve.
#2. Reset the idle or transmission air control valve.
The next troubleshooting approach would be to reset the car’s idle air control valve to enable it to work well until you get a replacement. The following steps will allow you carry out the resetting.
#3. Clean the idle air control valve.
Cleaning the idle air control valve can also help you troubleshoot an idle air control valve issue. Since carbon and some other contaminants can accumulate within the car’s idle control during combustion, cleaning the valve will help get the debris off.
Endeavor to search the car’s manufacturer’s manual to determine whether it is safe to make use of carbon cleaner to remove accumulated carbon from your car.
The cleaning will also require tools like a wrench, coverall, flathead screwdriver, star head screwdriver, and a new idle air control valve gasket.
Once the equipment is ready, kindly go through the vehicle’s manual and follow through with the guidelines for cleaning the idle or transmission air control valve provided there.
However, this is a generic procedure that can help you clean your car’s idle air control valve in a few steps.
Step 1: Identify the idle air control valve
Locate the idle or transmission air control valve to commence the cleaning process. It is located near the air intake by the engine side.
Step 2: Remove the electric plug behind the idle air control valve
Once you locate the car’s idle air control valve, use a screwdriver to remove the plug at the back of the idle air control valve.
Ensure to avoid breaking the plastic tang that holds the wire network in place of the sensor. It helps keep the wiring harness against vibrations that can get it off the sensor.
Step 3: Remove the idle air control valve’s bolts or screws
Now, remove the bolts or screws used in holding the car’s idle air control valve in place on the block.
Step 4: Hold the downward-pointing valve and spray the end
After removing the bolts, locate the valve pointing downward and use a carburetor cleaner to spray the valve’s pointed end. Ensure not to allow the carburetor cleaner into the valve’s housing. Spray the part over and over again until the carbon is entirely off.
Step 5: Fix the idle air control valve and the wiring harness in place
Once you are satisfied with the leaning, get the idle air control valve back in place and fix the wiring harness. Then start the car and find out whether it idles well. You can also find out how to clean idle air control valve without removing the component.
Driving With A Bad Idle Air Control Valve
Can you drive with a bad idle air control valve? While you may be able to continue driving your vehicle if it has a failing IAC valve, you shouldn’t do so.
Not only can a bad IAC lead to stalling while you drive, therefore obstructing traffic or, worse, causing an accident, but it can also place undue stress on your engine, damaging it.
An otherwise minor problem can quickly snowball into an extremely costly one if left unaddressed.
Since it compromises your vehicle’s operation, a bad IAC valve will likely make you fail a vehicle safety inspection. No joke — you will get an automatic fail once the inspector sees the Check Engine Light on.
Rather than wait for something bad to happen, have the faulty IAC inspected and, if necessary, cleaned or replaced.
How to Test an Idle Air Control Valve
Vacuum leaks and circuit problems can mimic a bad IAC valve. That’s why it’s a good idea to test a suspect IAC before you rush out and buy a new one.
Without a doubt, using an OEM-level scan tool is the easiest way to test an IAC valve. OEM-level means the scanner has most of the same functions as the dealer’s factory tool.
Code readers and OBD-II scan tools don’t have the necessary bi-directional controls to test an IAC.
OEM-level scan tools are awesome because, on many vehicles, you can directly control the IAC, taking the PCM completely out of the loop. Idle speed should increase as you incrementally open the valve, and decrease as you close the valve.
If the IAC does not respond to the scanner’s commands, the issue is either the IAC or its control circuit (excluding the PCM).
The problem is, most DIYers don’t have access to an OEM-level scan tool—which is why we’re going to discuss IAC troubleshooting with a code reader and digital multimeter (DMM).
Before beginning, however, you’ll want to have the vehicle’s repair information handy. Manuals, such as those from Chilton, are good, but an ALLDATA subscription is even better.
The latter has single-vehicle subscriptions for DIYers that provide detailed factory repair information.
Note: The following are general guidelines for educational and entertainment purposes only. Consult your vehicle’s factory information for specific repair instructions and recommended safety procedures.
Step 1. Check for Diagnostic Trouble Codes (DTCs)
Is there an idle speed or other IAC-related DTC stored? Then there’s probably a problem with the IAC, a vacuum leak, or a problem with the IAC control circuit.
In most cases, cars built after 1996 with onboard diagnostics (OBD) II will set a code for a bad IAC. Many older cars with OBD I will also set a DTC when there’s a problem with the IAC. You can check for diagnostic trouble codes using a scan tool or code reader.
These days, you can even get an inexpensive code reader for your smartphone.
Step 2. Perform a Visual Inspection
If you find IAC or idle speed codes stored, you can move on to performing a visual inspection.
You’ll want to look for issues, such as damaged hoses (creating vacuum leaks) and loose or broken wires going to the IAC. Also, check that the IAC’s electrical connector is clean and tight.
Repair any issues found during the visual inspection, clear the DTCs, and see whether the problem returns.
Step 3. Test the IAC Valve (Without an OEM-Level Scan Tool)
Because there are a variety of IAC designs in use today, there isn’t a one-size-fits-all way to pinpoint a failure on all vehicles. But the following tests will work on many applications.
Unplug the IAC Connector
On many vehicles, unplugging the IAC valve and listening for a change in RPMs will indicate whether the IAC and its circuit are intact.
Note: This test does not work on all vehicles. If you do not hear a change in RPMs, do not assume the IAC is bad until you do further testing. Also, this test may cause DTCs to set.
With the engine off, unplug the IAC. Then start the engine and listen for an idle speed that’s either too high, too low, or fluctuating.
Turn the engine off and plug the IAC back in. Restart the engine—idle speed should sound normal with the IAC plugged in.
An incorrect idle speed with the IAC unplugged (and a normal idle speed with the IAC connected) indicates the valve and its control circuit are working properly. There may be another problem, such as a vacuum leak causing your concern.
If you do not hear a change in idle speed, it’s possible that the IAC is faulty or there’s a problem with the valve’s control circuit (or this test does not apply to your vehicle).
Check the Resistance
One way you can check an IAC is by measuring its electrical resistance. Keep in mind, however, that this test is not conclusive. You’re only testing the electrical portion of the IAC, not the mechanical part.
To check resistance, you will need a repair manual and a digital multimeter (DMM).
Here’s how it’s done:
- Turn your multimeter to the ohms setting.
- Disconnect the IAC electrical connector.
- Consult a repair manual for the IAC resistance specifications and terminal identifications.
- Use your DMM to check the resistance between the terminals on the IAC (not the harness side of the connector). If the resistance values are outside specification, the IAC is likely faulty and needs to be replaced.
Remove the IAC and Check for Carbon Buildup and Debris
An IAC can be okay electrically (with good resistance values) but faulty mechanically. That’s why it’s a good idea to remove the IAC to check for excessive carbon buildup and debris.
You can try to clean the IAC with a throttle body cleaner. Afterward, clear any codes and see if the problem goes away and stays away. If the issue persists, you may need to replace the IAC, or there could be a circuit problem or vacuum leak you need to address.
Idle Air Control Valve Replacement Cost
Replacing a bad idle air control valve is as easy as cleaning a dirty one, if not easier, though you will need to buy a new valve.
The cost of an IAC valve will be around $70 to over $400 depending on the quality of the value and the make and model of your vehicle. If you decide to have a mechanic perform the replacement, expect to pay an additional $50 to $100 for labor.
So, the total replacement cost for an idle control valve at a shop can vary from $120 to $500 at a shop.
The procedure to remove and replace the old IAC valve is nearly identical to the procedure for cleaning a dirty valve (see above).
The only difference is that, rather than clean and reinstall the old valve after removing it, you would dispose of it and install a new one instead.
You will also need to remove the old gasket, clean any gunk that’s left behind, and replace it with a new gasket.
FAQs.
Q: Can you drive with a faulty IAC valve?
Yes, you may be able to drive with a bad IAC valve, but it is not safe to do so. A bad idle air control valve can cause a vehicle to stall consistently, which is not good for safety when driving.
If the bad IAC valve is not rectified immediately, the car may fail to idle as the engine is being affected. This is because the vehicle will no longer have a source of air that will enable it to maintain correct idle.
You may want to find out how to bypass IAC valve before taking your vehicle to a mechanic for proper repair.
Q: What happens if idle air control valve is stuck open?
If a car’s idle air control valve is stuck open, it will create a rich air-fuel ratio while the vehicle idles. Therefore, the car’s engine may start well while warm and run until it reaches a high enough RPM.
Meanwhile, the engine could also easily start when it is cold, but it will die in a moment after puffing off some black tail-pipe smoke.
In any case, a stuck open idle air control valve isn’t the best for your car. So, ensure to fix any abnormalities you experience with your vehicle.
Q: How much does an idle air control valve cost?
Replacing a bad IAC valve does not cost so much, as it is estimated to be anywhere around $120 to $500. The total cost consists of parts cost up to $70 – $400. At the same time, the labor cost is about $50 to $100.
However, the replacement cost depends on the make and model of the vehicle. The location and service provider are factors to consider when budgeting to replace a bad idle or transmission air control valve.
Q: Can a bad idle air control valve cause a misfire?
Several symptoms characterize a bad idle air control valve, especially stalling. Once the early signs are not noted and the idle air control valve fixed, it may result in more complicated challenges like random engine misfires.
Different malfunctions can cause engine misfires in a vehicle’s engine compartment. So, endeavor to find out what may be wrong with your vehicle’s engine whenever you experience an engine misfire.
Q: Can a idle control valve be cleaned?
Of course, an idle control valve can be cleaned to enable it to stay working actively. This is one way to prevent the component from becoming faulty, thereby saving you the stress of buying a new part for replacement.
However, some idle control valves may not be easily cleaned. Therefore, it is essential to find out if your car’s idle control valve can be cleaned without any complications.
Once this is confirmed, cleaning the valve can really help you save some money that a new idle air control valve may cost.
Q: How do you reset your transmission air control valve?
Resetting a car’s IAC valve may be the solution to a malfunctioning idle air control valve. To reset your car’s idle air control valve, follow the procedure below.
- Turn ON the car’s ignition
- Leave the car’s engine to run for some time
- Turn OFF the ignition
- Start the car without depressing the car’s accelerator
- Check the car’s idle speed
Once the steps above are followed, the ECM will automatically reset the car’s idle air control valve. After the reset, your vehicle is good to go with the idle air control valve working perfectly again.
Final Words
Idling air control valve symptoms are common signs that shouldn’t be ignored when they manifest. Otherwise, the consequence may be detrimental to the car and its owner.
So, if you ever experience the symptoms as unveiled in this article, ensure to follow the troubleshooting approaches recommended above. However, ensure to observe your vehicle manufacturer’s manual for proper guide in handling the component.
If you are not sure of fixing the problem by yourself, ensure to consult a professional auto mechanic to do the job. Fixing the issue will only cost a few dollars. It is easier and cheaper to manage problems when they have not escalated.