Stepper motor prob.

[xstriple]

Can anyone tell me how much movement there should be on the plunger of the switch when plugged into the loom (screwed out of the manifold) and the ignition cycled on and off please? My problem has been over revving on idle and gear changes when hot

[PhilipA]

It should completely retract when the ignition is turned off.

On start up it will step in /extend until the revs are near target so will probably do nothing if out of the manifold or may extend fully. AFAIR it will not move out if the ignition is just turned on but needs an engine rev signal to the ECU for the ECU to give step signals.

When cold the target is AFAIR 1100RPM and hot is 650RPM so it should move in and out to attain those revs.

The stepper moves from step signals from the ECU , and will not respond to 12volts or 5 volts.
You should also check that the kerb idle is correct by disconnecting the pipe from the throttle body and blocking the hole in the manifold and the end of the pipe, and the revs should be about 550 in a hot engine.
Regards Philip A