ICV issue

[Niall]

The ICV does a self test every time you switch on the ignition.

ECU "reset" is not required.

Your ICV is dead, the wrong type? (they're all the same though ) or you've got an air leak.

This. A ECU reset is not required!

Its always worth unscrewing the plunger from the ICV and giving it all a bloody good clean up with some brake cleaner. Sometimes it can bring them back to life but 9/10, it will only last for a few weeks or months then go back to its old ways.

I get insured in a couple of weeks so I'll take it for a drive and see if that settles it, I only put it in yesterday and drove for 1 minute in a car park so I don't think it had time to set itself up

It should only take a few seconds mate. The only way the ECU knows where the plunger is is by the MAP sensor value. As soon as it detects that its too high for idle, it will push the plunger out but if the ICV won't work because its fooked, instead of cutting the fuel and stalling the car, it just allows it to idle silly high or not at all lol.