Can a bad IAC cause an idle speed to go too high?
As you probably guessed, a faulty IAC can result in an idle speed that’s either too high or too low, depending on whether the device is stuck open or stuck closed. An idle speed that bounces up and down is also a possibility.
Can a bad IAC cause a DTC to set?
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.
How to clean the idle air control valve ( IAC )?
How To Clean The Idle Air Control Valve (IAC): One common problem is a buildup of carbon or fuel varnish deposits in the idle speed control valve. The cure for this condition is to clean the valve, with some aerosol throttle cleaner or engine top cleaner. Follow these common instructions: Disconnect the air intake ductwork from the throttle body.
How to test the coil driver circuits in the IAC valve?
How To test the coil driver circuits in the (IAC) valve: Using an ohmmeter, measure the resistance between pins 3 and 2 on the (IAC) valve. Resistance should be 10-14 ohms. If resistance is ok, proceed to the next step.
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.
As you probably guessed, a faulty IAC can result in an idle speed that’s either too high or too low, depending on whether the device is stuck open or stuck closed. An idle speed that bounces up and down is also a possibility.
What does an idle air control valve do?
In the not-so-distant past, nearly all cars had an idle air control valve (IAC). It’s a pretty simple device that controls idle speed by managing the amount of air bypassing the throttle plate. Some IACs are stepper motors, while others are solenoids.
What does it mean when idle speed does not change?
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). One way you can check an IAC is by measuring its electrical resistance.