Proj993

I have a '96 993 C2. Two weeks earlier I was not able to lock the car after parking. The car was perfectly fine after 20 minutes or so.

On Sunday, during a 15 minute drive, the stereo turned off and then on by itself a couple of times during the first 2 minutes. Then, a few minutes later while driving on the highway the car hesitated for a second with some of the dash lights coming on and then everything was perfectly fine. I parked the car, went into a store for 5 minutes and when I came out the car wouldn't start and absolutely none of the electricals even the clock were functioning. I towed the car to the dealer on Sunday.

The car was still dead at the dealer on Monday when they checked it initially. They couldn't get to my car to run any diagnostics until today (Tuesday). Now the car is perfectly fine again and they can't find anything wrong.

Before the initial incident I had noticed that the clock was slow by 30 minutes or so indicating the current stopped flowing occasionally. The Battery is about a month old and the alternator was replaced less than three years ago. The car runs perfectly fine otherwise. Any ideas?

Stealth 993

Check your battery cables. Then put a volt meter on the battery & start the car, is should be 14.4v. If not you might have an alternator problem.

Proj993

If there's a problem with the alternator, shouldn't the car not start (because of low charge on the battery) after the problem goes away? Once it comes back to life, it starts strong and is perfectly fine.

techman1

Please do not discount the effect an old negative battery cable can have. Is it old? I don't care if it looks good, replace it!

Sounds like I like wasting money? Wasted a lot of time in the past on my '95 chasing small gremlins. Someone pointed out the cable can look new, but will build up resistance. Best return for $12 bucks I ever spent!

1pcarnut

Good comments above regarding basic connections and grounds. Might also check and see if your car was one of the ones that was under recall for the wiring harness.

Stealth 993

Maybe, but in fact the car can run with out the alt at all, or even the battery once started.

My point is check the simple things, to rule them out. Only after checking can you rule something out, no matter how "new" it is.

A poor ground can cause all kinds of bad things!

Proj993

Is this an easy replacement? Do you happen to have a part number?

techman1

Nope, picked up mine at the local auto supply store. Took mine off and did comparison shopping. It helps to have it in hand, various sizes and styles are carried. At least the bigger stores have a good selection.
Additionally, another rennlister had complained about his intermittent no start issue. When the negative cable was pointed out, his next time having problems, he went and moved the cable a little, and it was able to start. You might try that next time the issue comes up.

techman1

And yes, easy replacement!

Proj993

Looked into this. Apparently the engine wiring harness was subject to a recall. I found the document (W301, you can google to find it). Cars built after January 1996 are supposed to be fine and not subject to this recall. Mine was built Feb 1996. The document lists related VINs and harness part numbers. I checked both and mine did not match. The symptoms listed in the document are:

"The deterioration of multiple wires may result in shorts which affect the proper function of the engine. Rough engine running, stalling, inability to start the engine due to a dead battery, starter malfunction, and illumination of the Malfunction Indicator Light (“Check Engine” warning lamp) are symptoms for this problem."

I have noticed all mentioned symptoms other than starter malfunction on occasion.

luvmy356

I had the same problem with my Targa last year. Radio would cut out randomly when cold which I thought was the radio faceplate getting loose..this happened for a few months. The one day on the highway, the car just hesitated, all the dash lights came on and then power came back. I turned around, and it happened a few more times until I got off the highway.

I drove it straight to my p-car shop. They ran diagnostics on it, checked all the cables and nothing was wrong. So they suggested we replace the DME relay which I did at his shop since my spare was with me. It has been fine ever since.

camlob

My wiring harness(94 993) looked like toasted noodles and eventually fried my ecu. I was using the car while waiting for my harness to arrive. Then kaboom! No more ecu.

Proj993

I checked my DME relay. It's part number is 944.615.227.00. I understand there's a newer version and I'll look into upgrading. Did you ever have a situation where you lost all electrical power?

Proj993

On April 17 I had another episode where the car would start, but would not idle without keeping my foot on the accelerator. This had never happened before. I replaced the DME relay and the ground cable on April 19 and the car has been perfectly fine since then.

Thanks for all the suggestions.