Pls Help - Random Cold Stalling

[JRuderman]

1987 Porsche 924s
65k - Excellent Condition

History: This car had a oil cooler leak which dumped oil into the cooling system. The car overheated. Head gasket blew. Repair: Replace thermostat, radiator, oil cooler, resurface head, and various hoses. Serviced by Porsche specialist.

Symptom: Car either hesitates (bucking) or will stall when driving for the first 10 miles or so when ice cold. Problem occurs randomly when cold, not everyday. Problem does not occur when car is warm. Car performs great when warm.

Troubleshooting to date: Replaced DME relay, swapped out DME ECU, swapped out Air Flow Meter, tested reference sensors, tested fuel output. Extensive vacuum testing revealed no leaks.

The odd thing about this problem is it started to occur after the head job was done. It appears to be temperature related. The problem occurs usually when it is cold outside and car has been sitting overnight.

Any ideas?

Thanks,

Jordan

[JRuderman]

Note that the car seems to idle normally when cold. No abnormalities in idle until the problem occurs:

Notes about the occurances: Car is running fine in the cold morning, and I usually come to a stopsign or light. I hear the DME relay click, and either the car will stall or will studder. The car will restart right away and appear to normal for the rest of the day. The problem may randomly occur under accelleration or at idle. Problem does not occur when car is warm.

Thanks for reading this and any suggestions you may have. This problem has been ongoing for the last 6 months and poses a road hazzard in the mornings.

[kukunaokala]

You did not not mention accessing codes. That's step one in most every mechanic's trouble shooting strategy. An '87 (I own an '83) anything without code gathering? Jeeezzzz!!! I will be dissappointed Dr. P.

They're starting to make interfaces between the ECU and that big'ol connector. The fee will be big, the machine is like $40k, but it will find your glitch.

My mantra when working on an auto is, "check your connections." Good luck and aloha, Neal

[This message has been edited by kukunaokala (edited 03-28-2001).]

[kukunaokala]

Re-reading your post, maybe you won't need the hi-tech, big buck diagnostic solution. Find out why your DME relay clicks. Spring is here for some parts of this country.

A friend's ignition coil's primary circuit resistance was off one ohm. Replaced the coil and now he's a happy camper. Good luck and aloha, Neal

[JRuderman]

The 924s ECU does not have the ability to store fault codes, unlike later 944's.

However I do have an update:
After driving home at night this evening, I popped open the hood with the engine running. I noticed arcing from the spark plug wires to the top distributor (near where the wires are routed). It seems as though the wires are "leaking".

I have to return to the shop tomorrow to return the known good DME ECU. They were planning on replacing the Thermal Sensor on the head. I think the wires may now have a better chance of solving the problem.

Any additional advice?

Thank you for your assistance.

-Jordan

[JRuderman]

After driving the car home this evening, I popped open the hood with the engine running (hoping to find something).

Well since I was working with a Maglight, I flipped off the headlights and my flashlight. Low and behold; I noticed the spark plug wires arcing in 2 places. One is where the wires wrap around the distributor, and the second location was near the intake manifold.

I was planning to go back to the shop tomorrow to return the test ECU that they loaned me. They think that it might me the temperature sensor on the head. I am going to request that they replace the wires.

If the wires are causing the problem, then why would it happen only when the car is cold?

Any other suggestions?

Thank you very much for your input.