Bouncy revs

[edjay]

Please help

I have a 90 spec gti 8v. Whenever I pull up to a stop the revs bounce up & down between approx 700 - 1500 rpm before eventually settling down to 800 rpm. Also the clutch & throttle have become very stiff, will replacing the cables sort this out

[richandhazel]

Not sure if the 90 spec gti has an ISV (Idle Stabilisation Valve). If it has, it might be worth giving that a clean. Its a common problem on the Audi's that had that fitted of that age. If I get time, I'll do some research later, I think my Bently will cover that model.
Throttle cable, I would try disconnecting it from the throttle housing and see exactly how free it is. Should then be able to identfy whether it is the cable or the throttle itself.
Clutch cable, I would first check that it is routed correctly, if it is then maybe do the same thing and disconnect it from the arm on the gearbox....see how free the cable is.  I know they can tend to bind up a little at the top of the adjuster.
Good luck

[jv]

I used to have an '89 16v and the idle stabilisation valve needed replacing on that. Coming up to a road junction, as you slowed down the car would just randomly cut out completely! Made for some very interesting moments...

jv

[richandhazel]

Just grabbed this from my Bentley (Bentley is a workshop manual that is far better than Haynes in my opinion):-

'All 1985-1986 models are equipped with either CIS or CIS-E fuel injection. Most 1987 models are equipped with either CIS or CIS-E. Small numbers of 1987 models and all 1988-1990 models are equipped with the Digifant II engine management system. 1991 and 1992 models, except in California, are also equipped with the Digifant II system. 1991 and later California models are equipped with the Digifant I system'

From this I assume you have the Difigant II and therefore you do have an ISV.

I think its worth checking and giving your ISV a clean, there is some information on it here, the first paragraph should prove helpful :-

http://members.lycos.co.uk/richandhazel/ISV/index.htm

Let me know if you want any more help, there are all kind of schematics, diagrams and text explaining what it does and where it fits in with all the other components etc.

From what I remember on the Audi forum, most people fixed erratic idle by simply cleaning it.

[edjay]

cheers lads... ill try it out & let you know how i got on

[edjay]

Havin some trouble removing the ISV valve, does anyone know how this is done ?

[richandhazel]

Not done it myself, I'll look it up and see if I can find some info for you.

[richandhazel]

Couldn't find much, how are you getting on?

[romney]

Try adjusting the air mixture first as this often fixes the problem. Failing that a new idle stabilisation valve is on the cards. Replacing this makes a great difference but can be expensive. Make sure you order one with the correct part number as there are plenty that look similar but are not.Removing the valve should be a pretty straight forward process.