Do all mk2 8v GTI's drop below idle before settling at idle when stopping??

[16vLeroy]

Try cleaning the throttle body. That always helps on my AGG engined Ibiza. 

[dadrathers]

Just sorted the same problem on mine. There are two throttle switches - one on top of the throttle body and one invisible underneath. The latter controls the idle. Open the throttle by hand with engine switched off. As soon as it opens a hair's breadth you should hear a slight click. This is the idle control switch. If you don't hear it then either it needs adjusting, you're deaf or you need a new one (not cheap, both switches have to be bought together - about £40 I think) Anyway get the Haynes out and that tells you all about it.

Good luck

[rubjonny]

As dadrathers says on a digi 8v the idle switch is underneath and is a pain to get to.  You can also test the switches electrically, as well as the ecu idle function without messign about with multimetrs and the like. run the engine and open the throttle by hand slightly so its reving just over idle speed, then press the WOT switch on top. the revs should then drop, then rise again when you release the switch.  This proves that the wiring to the plug is fine, the ecu is fine and the isv at least works a bit!  This works because the 2 switches on the throttle body are wired in parallel, the ecu can tell the difference based on revs and/or the signal from the air flow meter