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Neil924 · Joined: 18 Mar 2003 Posts: 4225 Location: Canada

A 1988 924S, has been running fine but recently at idle the rpms drop, then come back up. It sounds like it isn't getting enough fuel, and is about to die, but it never does. It just has a really rough idle, however under acceleration and cruising it acts perfectly fine. Any ideas? I was thinking maybe a fuel sending problem (i.e. fuel pump).

Any ideas?

P.S. It's not my car. Could it be the injectors or timing or air fuel mixture?

Thanks.

Neil

gohim · Joined: 02 Nov 2002 Posts: 4459 Location: Rialto, CA

The problem that you describe is a classic symptom of bad engine mounts.

edh · Joined: 19 Nov 2003 Posts: 240 Location: Derby, UK

Could possibly be lots of things apart from mounts

Does it vary between hot & cold running?

If you hold it on the throttle at 1k rpm do you get any vibration?
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current - '90 944S2, '00 986S,
ex - '90 944 turbo '86 924S, '88 924S

Neil924 · Joined: 18 Mar 2003 Posts: 4225 Location: Canada

Thanks a bunch.

Techno Duck · Posted: Sun Dec 18, 2005 3:51 am Post subject:

Neil, do the RPM's fluctuate or do they stay constant? If they stay at a constant the normal idle RPM (about 900) then its probably your engine mounts. If it idles very low, it could be a idle stabilizer valve or your TPS.
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1987 Zermatt Silver Porsche 924S <-- Sold in Nov. '04
1987 Guards Red Porsche 944 <-- Sold in Jan. '08
1988 Guards Red Porsche 951 <-- Das Boost

Llamaguy · Joined: 02 Jul 2003 Posts: 711 Location: Indiana

check the fuel pressure regulator and the dampener, sounds like what was happening to mine.
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1987 924S Guards Red
1997 Suzuki Tl1000 Supersport

Slam · Posted: Fri Jan 27, 2006 5:21 pm Post subject:

Does engine temperature affect it? Will it idle properly if the throttle switch is adjusted so it doesn't send an on-idle signal?
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'88 944 Auto - may or may not resurrect