924Board.org

[dgeades]

The idling speed of my 1981 924 Euro generally sits at around 400 rpm according to the tachometer – in reality, I reckon its nearer 700 rpm. Sometimes though – about 30 minutes after a cold start – the idle speed rises and stays at 2000 rpm. I adjust the idle speed (by twiddling the screw on the throttle housing) back to around 400 rpm and its fine again. The next time I start it though it won’t idle at all so I have to twiddle the idle screw back to where it was before……and so it goes on.
I’m guessing that this is caused by a sticky aux. air valve. If so, can it be repaired? If so how do I go about it?
Any (all) suggestions welcome.

Cheers

[Diesel]

Did you clean the carbon from around the throttle valve(the big plate in the throttle body)? Try that first.

[Roger Hall]

i had the same exact problem then on day the idel was rough and i heard a leak the idle screw had come out completly and was missing i went to he junkyard got an idle screw from a jetta and repalced it ive never had the problem since cheap fix and its a german part

[Joes924]

I had that happen a couple of times also befor i switched the ignition and wires hasnt happend all winter though.

[dgeades]

Diesel: The throttle plate is as clean as a whistle.
Roger: The idle speed screw is still there where I left it.
The auxiliary air valve itself works just fine (30 ohms approx., opens and closes like it should) - the problem is with the connector. Half of the connector has been broken away and it’s only been held together with dirt. I guess the contact has been intermittent at best. I’ll get a replacement from the scrap yard but, for the time being, I’ve just cleaned it all and taped it back together. It’s worked fine over the 140 miles/6 start-stops done today.
Thanks anyway.

[Roger Hall]

im not suggesting that your idle screw poped out like mine im just suggesting that it may be seating properly and its vibrating loose i fiddled aroud with mine for awhile and had the same symptoms you describe pull yours out clean it and wrap some plumers tape around it cant hurt to try and it would not cost much i would not have replaced mine if i had not lost it but after it was replaced the problem dissapeared cheap and simple to try

[dgeades]

Roger,

What I meant was that the idle screw was still in the same position - it hadn't vibrated in or out. Should there be a cover over the screw? There seems to be a housing machined in the throttle body although this has been mangled by some previous owner.

[-nick]

the idle screw should have a little rubber oring that keeps it from vibrating in and out. you could probably find one at a hardware store- or else it's less than a dollar at the dealer (this will probably be the only time you'll ever see those words). and it works a little better than teflon tape!

regards,
-nick

[Roger Hall]

there is no plug over the screw it just sits down inside the opening if its not the screw it could be a vacum problem get some brake cleaner and spray it around the intake ports and rubber lines if there is a vacum leak then it will suck the brake cleaner in and the rpms will rise