What causes idle surging?

What causes idle surging?

If an engine is not getting enough fuel (this is called “running lean”), due to fuel pressure (regulated by the fuel pump and regulator), restricted fuel injectors, a vacuum leak or really anything that throws off the fuel mixture going in to the engine, this can cause the surge.

How do I relearn my IAC valve?

A. Idle Relearn

1. Start the engine in Park/Neutral. Rev the engine to above 2,500rpm and hold for 10-15 seconds.
2. Slowly reduce throttle back to idle.
3. The ECU should now begin to learn the idle position (you will hear the sucking sound through the throttle body change as the Idle Air Control Motor changes position).

What is erratic idle?

Erratic engine idle can be caused by various factors, but the most common and likely cause is a dirty or malfunctioning Mass Air Flow (MAF) sensor. This is a device found in fuel-injected cars and measures air flow so that the appropriate amount of fuel can be injected.

Do you have to reset a IAC valve?

If the valve exceeds the specified measurement, press firmly on the valve to retract it. Turn the ignition ON and leave on for several seconds then turn the ignition OFF to allow the ECM to reset the IAC valve. You should be good to go. If you need to adjust your minimum air (idle speed), click here.

How to fix the idle air control valve ( IAC )?

Start the engine, then increase and hold the idle speed to 1,000 to 1,500 rpm. Spray the throttle cleaner or engine cleaner into the throat of the throttle body; aiming for the idle air bypass port. Turn the engine off to allow the cleaner to soak into the (IAC) passageway. Wait about three minutes.

What should the resistance be on an 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. Finally, if resistance is out of range, replace the (IAC) and retest.

How can I control the IAC on my car?

On many vehicles, you can directly control the IAC, taking the PCM completely out of the loop, by using an OEM-level scan tool. 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).

Can a bad IAC cause an engine to stall?

A faulty IAC can starve the engine of air at idle, resulting in stalling. Although rare, there are instances where a faulty IAC can throw off the air/fuel mixture enough to prevent the engine from starting. Vacuum leaks and circuit problems can mimic a bad IAC valve.