Topic

Resetting the IACV.
Reason for resetting - The throttle has a sensor on it (TPS - throttle position sensor) that sends a 'voltage' corresponding to its position to the MEMS unit (Modular Engine Management system). This tells the computer the current position of the throttle ( ie; How much throttle you are applying) This enables the MEMS unit to calculate the correct operating parameters ( Fuel / Air mix etc).

It is important the MEMS unit knows the absolute minimum and maximum input voltage it will see on the full extent of throttle to enable it to correctly know the current position it's in. We do this by resetting it.

How to reset the IACV.
If you find that the idle speed is 'hunting' or high, try resetting the throttle position sensor (TPS). Here's how you do this:-

Warm up the engine to its normal operating temperature (the engine requires extra air and fuel when cold). This is actually what the IACV - idle air control valve manages.

Switch the ignition to position 2 so that all the dash lights come on but don't start the engine up.
Press the accelerator down slowly to the floor 5 times in 30 seconds.
Wait for 15 seconds.
Turn off the ignition.
The TPS has been re-set and the engine can now be re-started.


You could give this a try before you clean or replace the IACV /Stepper motor. But you should also do it after you have done either of those two jobs as it apparrently allows the ecu (engine control unit) to re-learn.

IACV - Removal, cleaning and replacing the valve by David Aiketgate.
IACV - Replacement guide by CJJ (Clive).

So doing this with a completely cold engine is likely to create a different result to doing it warmed up?

Warm up the engine to its normal operating temperature (the engine requires extra air and fuel when cold). This is actually what the IACV - idle air control valve manages.

I'm guessing, probably not at this time of year. But I warmed it up anyhow. If it happens again, I'll try it from cold and get back to you.