993 intermittent starting problem

kirschs · 11-05-2006, 03:06 PM

I need some help with a very frustrating problem with my 95 993. I bought it two years ago from Barrier Motors, a Porsche dealer. It has 75k miles on it and had always run very well till the last three months. It has developed an intermittent starting and running problem. It has been at a reputable Porsche shop in Seattle for the last month and he has not been able to diagnose the problem.

These are the symptoms. Occasionally it will not start, it cranks over but will not fire. It will occasionally die while driving. When it dies the tach goes to zero and it will start up again. When it will not start, if you let it sit for a while it will eventually start. I called the dealer and was told that the wiring harness recall has been done, they claim it was anyway.

The mechanic says that when it will not start it is not getting a spark. He has replaced a relay that as I understand it, is a common problem with this car. He has disconnected an after market alarm system. He has adjusted the sensor on the flywheel. When it does not start there are no fault codes. After it sits for a while and starts some of the warning lights, such as the check engine light stays on for a while. The mechanic is well known and reputable. He and I are frustrated by this naturally. The car had a complete tune up about three thousand miles ago at the shop where it is now which included two new distributor caps and it ran very well for a couple thousand miles. Once when it would not start he swapped out the central computer and it still did not start. I am sure he has checked numerous other things.

Does anybody have any advice for me?

Thanks,
Steve

AFJuvat · 11-06-2006, 05:02 AM

Is the car at Gerber Motorsport?

Ignition control module under the drivers seat, behind the DME.

As they age, they intermittently cut out.

This module was specific to the 1995 cars.

993.602.706.00

AFJ

ANTONIO · 11-06-2006, 07:41 AM

Check your DME relay, notorious for failing, cheers, Ant.

kirschs · 11-07-2006, 05:56 AM

Thank you for your advice, I will tell the mechanic.
Steve

kang · 11-07-2006, 07:54 AM

I think the relay that your mechanic already changed, the one you mention in the first post, is the DME relay.

kirschs · 11-07-2006, 01:24 PM

Yes he said that was a common problem and that was the first thing he replaced. I called him today about the ignition module and he said he thinks he has fixed the problem. He thinks it was a bad connection on one of the battery terminals. It sounded a little puzzleing to me but he seems pretty confident. He said he could recreate the problem by moveing the wire. I am supposed to picik it up tomorrow so we will see.

Thanks again for the advice.
Steve

rfeierbach · 11-10-2006, 06:42 PM

I had the exact problem with my 1990 Porsche. I replaced the DME relay, which is located in the luggage compartment up front, where the fuses are, and my problem went completely away. The part costs about $30, and you can enjoy your car again! Good luck.

Robert

rfeierbach · 11-10-2006, 06:45 PM

Also check your engine block grounding, to make sure they are still good. This is another known problem, which causes the DME relay and/or electric pump to malfunction.
Regards,
Robert

cehensley · 11-17-2006, 10:42 AM

I'd check to make sure your chip is fully seated. I just bought a chip upgrade from Steve at http://www.rennsportsystems.com and he told me if I didn't seat the chip properly that I'd get intermittent problems starting the car and it would possibly die while driving...