924Board.org

[staticsan]

It's happened twice now.

I've gone for a drive and after a while (after it's hot) I notice that when the 924 idles, the idle speed is something like 500rpm. So when I get home, I find a screwdriver and raise it by turning the screw on the side of the throttle body.

Next time I go for a drive, the same thing. Again, I adjust the idle screw when I get home, taking it back up to 950. This time I put a dot of paint on the screw head to see if it moves. But why should it move?

I did notice that there is a bit of vacuum around the idle screw. Isn't there supposed to be a rubber cap, like over the mixture screw? Could that vacuum be pulling the screw in and lowering the idle?

Wade.

[CorsePerVita]

I just took mine out and looked at it. Looks like it has a rubber O-Ring below the head on it that helps keep it in place (at least on mine). If that were to crack or shrink or go hard it could get loose and start to back off or move or vibrate.
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- 1977 Porsche 924 2.0 N/A (Trackday Project)
- 1979 Porsche 924 2.0 N/A (The other daily)
- 1980 Porsche 931 (Daily)
- 1987 Lamborghini Jalpa
- 1999 Ducati 900SS

[tyfighter123]

Vibration gets it. When I was breaking in my engine my screw keep vibrating in making the idle much higher.
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Porsche 924 1977 N/A
Mustang GT/CS 2007
Porsche 924S 1987 (parts car)(cut up and recycled)
Porsche 911S 1976
Porsche 931 1980
Porsche 931 1980 (parts car)

[staticsan]

The rubber o-ring just behind the head was old and hard. Replaced that and it keeps its idle speed now. So simple.

Wade.

[CorsePerVita]

Rock on!
_________________
- 1977 Porsche 924 2.0 N/A (Trackday Project)
- 1979 Porsche 924 2.0 N/A (The other daily)
- 1980 Porsche 931 (Daily)
- 1987 Lamborghini Jalpa
- 1999 Ducati 900SS