Davies

Good info to know Steve. I must say, I quite like the theatrical drama of a bit of smoke pouring out from under the wheel wells when I'm idling at a light :-)

Synapse120

Jim at hendrick Porsche was able to isolate the problem to being the ECU by running the connector for injector 5 on the 6th cylinder injector and verifying proper operation of the injector.

So it is safe to say that this is a bad DME causing the injector in cylinder 6 to continuously pump gas into the cylinder when the car is on.

It is surprising that the DME went bad from the car sitting, but low voltage to the DME (due to the weak battery) could account for computer issues.

I'm sending the DME to 911chips.com for repair, if anyone has experience with them good or bad I would like to hear about it.

IXLR8

If I remember, the injectors get 12V power all the time and the Motronic "sinks" the individual injector conductor to turn the injector on.

A simple component replacement I would think or maybe a bad solder joint. It should not cost much.

Steve Weiner-Rennsport Systems

HA,...I do like white smoke boiling off the tires when I step on the throttle, but that's a totally different experience.

The blue stuff, not so much.

Ewok

The problem with these older Porsches is that when they catch fire, it seems wrong to put the fire out with water.

Always keep a small fire extinguisher in the car (tied down / mounted). Expecially in a car like a 993 that can't just be replaced!

Synapse120

I didn't put the fire out with water, i used my hands and the smother technique (I know that is stupid, but in the heat of the moment with no water or fire extinguisher it was the only thing i could think to do).

A fire extinguisher has been purchased for the car (lesson learned).

pp000830

rtuing

Clutch starting cars in the old days always shot a lot of unburnt fuel into the exhaust system. Not sure about what happens with electronic fuel injection.
Andy

deactivateduser66

Afterall, so is it a good idea to keep an extra DME relay by the glove box after long periods of storage?

http://www.fvd.de/de/en/Porsche-0/99...Relay_DME.html

A question though, why have you send your DME for a fixup instead of getting a spare and simply replacing it? In summary, was the whole ordeal based on a bad DME relay because of storage?

Hope everythings tiptop on you side!



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KNS

A spare DME relay is about $40. A spare DME is a couple thousand bucks.

NineMeister

I would still not be 100% certain that it is the ECU. The injectors are all wired with switched 12v and are earthed through the ECU controller. A wire break or short to ground in the engine wiring harness could cause the injector to fire continuously once the 12v feed switches live. Ask them to run a new wire from the injector wire at the ecu and a 12v supply to a noid light, if the light stays on then yes, 100%, you need a new ECU or ECU repair.

deactivateduser66

That is some awesome information, thank you!

deactivateduser66

Yep, that's why I thought, thanks for clearing it up.

Synapse120

I got the car back on Tuesday after getting the ECU repaired, spark plugs changed, O2 sensor replaced and an oil change and its running perfect.

Now i just need to remove and repair the bumper and the car will be in a good place.

Thanks to everyone that provided their technical expertise, i really appreciate it.

pp000830

Very unlikely it is the DME computer. Dealers do not know how to service much less diagnose a 993s as they haven't sold on of these in 17 years or serviced one under warrenty in many years. Get the car to a good independent who works on older Porsche regularly. Seems from the thread you have not found the root cause. Injectors can stick open but I believe your problem is likely much simpler than you think. Lots of conjecture here, you need facts. Find someone who can get some.