what have i done

[rockhopper]

just bought a mk2 8v '92',drve home yesterday and the idle sat at either 900rpm or 1300rpm.today i took off the isv and gave it a good clean out with carb cleaner,refitted it but now the revs are screaming up and down 1000-2500,i have cleaned again and checked all the hoses but still does it?if i pinch the top hose the idle settles down but then goes mad again when i let go i hope you guys can help me out as i wished i had left it well alone thanks

[Leon R]

Did you let the carb cleaner dry out or blow it out with air?

Are the hose connections tight for all vac hoses?

I'd set it up again for fueling with rubjonnys guide, then maybe donor a working isv. Sometimes cleaning it with petrol can ruin the rubber seals in the isv, if you leave brake cleaner in it for too long it can do the same.

[rockhopper]

thanks,i am going to bring a multimeter home from work tomorow and check it over.i just cant believe its gone from a minor prob to to as bad as it is.any other ideas,what controls the isv and could the problem be there

[gti_copey]

i have the same sort of problem on mine mine if you leave it on idle it feels like it wants to die but when i rev it its fine again 

[rockhopper]

this just keeps rising and falling 1000-2500-1000 and reving it doesnt clear it.

[rubjonny]

Check the idle switch its underneath the throttle body.  Check that it clicks, if it doesnt, loosen the mounting screws and move it till it clicks
It can also be caused if the throttle cable is too tight, so before you move the switch make sure the throttle it hits up against the stop firmly.  Also look behind the throttle body, the plug round the back is for the throttle switches, the wires often snap

Once you've done that, tune it as per my guide:
http://www.golfgtiforum.co.uk/index.php?topic=33253.0