964 problem

[pingpong]

Hi, i own a 1990 964 C2 5 speed with at first a small problem, LOL.

The car starts drives and than dies. Starts again and over and over the same, the car runs strong when running before it dies.

I have of course changed D.M.E., checked Oxigen sensor, battery connection, fuel delivery and now?

Brought it to my favored reliable Porsche shop in the PHX area, they think its the alarm. Fast forward now after many month's they cant find the problem either, not that they give up but i am getting worried about the cost.

Please anybody with the same problem? or fix? for sure getting desperate any help highly appreciated.

Thanks.

[964TargaC2]

If it is dying when warm/hot it could be the coil(s)...just a guess

DO NOT Replace with Bosch Silver coils (which is about all there is now) Use the 993 coil pack, , you will need the 993 coil connectors to put on your coil wires

[RedCoupe]

Does your shop have a Bosch Hammer or software such as Durametric so they can check for trouble codes?

[pingpong]

going down on Saturday to talk with the shop and ask questions.

[pingpong]

Yes my shop has the Bosch hammer.

They changed out all electronics from other clients cars to test but its not solved so far.
They are confident to fix the problem, again i am just worried about $'s spend.

At hindsight i should have tried harder myself before bringing the car to my trusted shop as it seems an easy fix if checking all/or/and all logical documented 964 problems, but i did not.

Please this is not a complain against the P Shop as i have been treated and with me a lot of other PCA members super good/nice/fair before and i like the owner and staff a lot.

Now what to do? take the car out of the shop? pay the bill aughh....for many, many hours without any results? waisted $'s and then try myself to fix?

Any suggestions, only thing i wonder that they focused many, many costly hours on the 964 alarm system as the culprit and understandable not wanted any suggestions from me and many knowledgeable Porsche 911 friends with suggestions, like your Doctor, please no.

Thanks.

[KNS]

You could politely ask them is they would be offended if you took the car to another shop so they could attack the problem from another angle. They might be perfectly fine with that just as it wouldn't be their problem any longer.

[Green993]

Just gonna throw this out there as it might help. My 993 did the same thing. It would start and about 15 minutes later it would die and not re-start until the engine cooled down (about 3 to 4 hours later). It drove me nuts. I tried all kinds of things- Fuel pressure, regulator, pump, dme relay, tested spark, changed out caps and rotors, checked codes, etc... All of this after I had just rebuilt the engine.

In the end somebody suggested I swap out the Flywheel sensor (AKA Reference sensor) and that did the trick. I later learned that the engine will start because the DME will use other sensors if the flywheel sensor is not sending readable info. Then after a brief period it will switch back to the faulty sensor and wham - STALL. Something to do with closed loop and open loop electronics FWIW. For some reason a code was not sent to the DME! You can check the operation of the flywheel sensor signal but you need an oscilloscope, something most shops have. You might want to mention it to them.

Anyway good luck, you'll get to the bottom of it.

[pingpong]

thanks & appreciated, going to mention that to the shop.

keep you posted.

[Newsboy]

I've never heard of other sensors taking over for the flywheel reference sensor, maybe Steve Weiner can address this. You don't need an Oscilloscope to test it. To test this, you can opened the DME relay(under the driver's seat) and used a multimeter set to AC voltage, across pins 47 & 48 of the large plug. iT's supposed to read 3 volts. When I tested mine, I got 0 volts. I suppose one on the way out could cause intermittent problems. This test is described in Adrian's book.

[pingpong]

Newsboy thanks, yes i agree with you.
I would appreciate if Steve or those with experience, chime in.
The shop has 30 hours into it now but no cigar, brrr.
No complaint as i have been treated very nice fair before with my other Porsches maintenance/problems.
Just want my car back running again with possible minimising further $ spend, please help.

[Green993]

From the Shop Manual

Test point 4
Rpm signal
Fault code 1_18
Run test using an oscilloscope. Connect and adjust shop oscilloscope
according to manufacturer's instructions.
Connect oscilloscope test lead with terminal 49 and terminal 48 of
the disconnected DME control unit plug.
24 05 DME Diagnosis I Troubleshooting 24 -33
Fault, Fault Code Possible Causes, Elimination, Remarks
Start engine. Sinewave fluctuations of 3 V min. must now be displayed.
An intermittently higher amplitude indicates the reference
mark signal.

[Mr.Alex]

Does it die while driving or on idle? If on idle, did you check the idle control valve.

[acar24]

Have you determined for sure that it is a fuel problem? IE when it dies spray fuel in the intake does it start? if so check fuel pump out put volume, after stall. - may have fuel pick up screen getting plugged, pressure regulator, or bad temp sensor. = harness ground. = DME? = Injector pulse. determine if it is fuel control or electrical. good luck, LA

[997Sbeebe]

you should sell the car to me and get out from underneath that LEMON!!

[Paperboy]

Have you/the shop solved the problem? Does it die when warm and then starts and runs fine once slightly cooled down? Had a sim prob, turned out it was a corroded gearbox/ chassis earth strap. Enough contact when cold but once engine/gearbox warmed up expansion made any contact disappear. Just a thought. Sure the shop would have checked this.

[ischmitz]

To the OP:

The flywheel sensor can become intermittent before it completely goes and this can be temperature-sensitive. It's an easy test though. Run the car until it dies, then disconnect the DME (55-pin connector) and measure between pin 47 and pin 48 with a voltmeter set to AC voltage. You should see ~ 2V while cranking.

While the shop might have swapped put control boxes without luck I wonder if they ever went as far as swapping the sensor. If your shop has access to a Hammer or PST-2 have they ever been able to pull any fault codes from the DME?

Another thing to look into is the ignition switch (electrical part). If there is an intermittent contact it could momentarily cut power to the DME. However, this would happen at random rather than after a certain run time.

Ingo

[ischmitz]

any updates - curious

[heliolps2]

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