My '92 C2 has 60k on the clock. All stock engine and exhaust, I bought it 4 months ago at 54k and it has always ran like a clock until just recently. A very well maintained car it is.

The rear window got broken out a month ago and the car sat in my shop for 10 days or so waiting for the new glass. I drove it to the glass shop and they installed the new glass. I picked it up that night and immediately it didn't like to start cold or idle either. Also, engine check light on. I drove around the city a bit and suddenly it seeemed better, but still the check light would stay on at times after starting and eventually go off. The car had never acted like that before in my ownership.

I went to my favorite Seattle shop, Gerber, and we all came to the conclusion that the battery went flat while waiting for new glass and it just hadn't fully charged. I charged the battery and all seemed well for about 10 days and the same symptoms returned.

Back to Gerber and this time it was for sure the alternator was toast. New alternator and battery just for grins and car runs way better for sure. Cranks faster, heater fan faster, etc.

However~

I still get the check light about half the time when starting the engine. When it goes on, it stays on for maybe 30-45 seconds and usually the idle is pretty rough and will die when you come to a stop. Also, the idle seems to surge or fluctuate more than I remember when I bought the car even when the check light is not illuminated.

The tech at Gerber is a good friend so we have made arrangements to swap cars and he is going to have it for as long as they need. I have the 911 Enthusiasts Companion and the troubleshooting area has quite a few things to check for idle problems although I'm not seeing a section for the engine check light.

I'm fully confident Gerber can get it sorted but if anyone has an idea to help them out that would be swell. Thanks~

 

do you think the glass took it out for a test drive and drove it hard and did not say nothing to you??

 

No way. The glass shop in question is completely professional and I know them as well. They do all the Porsche glass for all the independant shops in Seattle.

 

Have you gotten the fault codes from the car after the check engine light comes on?

 

Thats the puzzler. They have plugged in the hammer and the computer didn't have any engine codes stored after any of these repairs.

 

I know this might seem silly ... but have you tried a simle DME reset yet ?

 

You might try this: Remove the negative battery cable and clean both ends of it thoroughly. also clean the connection on the body where the negative battery cable attaches. Fixed a similiar problem for me.

 

Thanks for the good suggestions thus far.

What is a simle DME reset? Did you mean simple DME reset? If so, what is the procedure for that? I replaced the relay when I first got the car as preventative maintenance.

 

Richard might have hit the nail. Have a look at this thread
Do they still sell the best smoked salmon bread rolls in the world on the wharf?

 

Thanks again guys.

Well, I just cleaned the connections and no change. The cable itself does have some greenish/gray nastiness on it where the cable disappears into the connector on the vehicle side. I'll try a new one tomorrow and see what happens.

At least the now the symptoms are occuring much more often and if this isn't it hopefully the shop can track the fault down easier as a result.

And yes the Seattle waterfront still has the best salmon-related anything.

 

I had a problem with the car turning over but not wanting to start......figured i was in for a new DME but tried the next day and it fired up as normal!

Did the cleaning of the terminals etc and all was fine for 2 weeks then the problem came back......removed the earth cable replaced it with a brand new one (old cable looked absolutely fine) and no more problems for 4 months now.

Still using the same DME but i carry a spare now just in case.

 

Found in the DIY Section ...

Unsteady idle? Engine feel like it's missing a bit? Slight lack of power? Try a DME reset. It's free, doesn't cost anything, and you get a good excuse to go for a drive!

1. Disconnect the negative battery lead for at least 15 min.
2. Reconnect the battery. Make sure the leads are tight on the posts.
3. Start the car and let it idle for 2-3 minutes.
4. Go for a vigorous drive, engaging all the gears and attempting to use the entire RPM range for each one (I said "attempting". Don't get arrested. )

This DME reset should reload the ignition maps inside the DME, and should hopefully cure any minor ailments. An alternative to this method is to borrow/buy a Hammer and do a manual reset of the DME, or to take the car to a shop that has the Hammer and have them do it.
Brian

 

Replaced the negative cable today and on restart the engine idled horribly and the check light was still on, so I thought it was no different. Then I let it run for a bit and the light went off, the idle hunted up and down pretty crazily, and then settled. This time the idle was back to what I remember when I bought the car. Almost perfectly rock solid with liitle or no variance.

Drove around a bit, shut it off and turned it on, one time it did the rough idle with check light so I thought to try the DME reset.

Went back to the shop, Gerber Motorsport, and the service writer Mark and I played with the hammer gizmo and did the reset.

Since then, the car is working perfectly. Rock solid idle, engine check light goes off the moment you select the "start" position of the key, etc. I'm holding my breath but it feels like we got it. Still have yet to try a start from stone-cold.

One thing my guy noticed while we played with the hammer. The ignition timing was registering at 3.7 degrees and he said it was supposed to be 0.7 degrees. The timing would change to 5.2 degrees sometimes with electrical load, just for a heartbeat. All other readings with the hammer were perfectly normal, he tells me.

He says we should check that out further. Anyone have any insight here? I thought my car was bonestock, OE chip, exhaust, etc. One random thought was maybe the car does have an aftermarket chip hence the advanced ignition timing.

 

Got an update after many trials and tribs.

Thus far, the car has a new alternator, battery, ground strap, O2 sensor, idle air control valve, caps & rotors, spark plugs, dist belt. Also checked the valve clearance and changed the oil just for grins. Reset the computer with the 'hammer tool a bazillion times.

The darn thing runs like new, EXCEPT, the check light still comes on at times right at startup. Normally goes out after 30-45 seconds although sometimes it won't. When the light is on, the car usually will just barely idle or not idle at all with the tach jumping up and down. One time we got it to happen with the 'hammer hooked up and it showed nothing strange other than the computer trying to compensate (advance) the ignition timing while the engine was going ballistic.

Gerber Motorsport now has the car for the duration to get this licked. I'm pretty sure they are going to try the tried and true parts swap/process of elimination with the spare complete 3.6 motor and such they have lying around.

Another symptom that very rarely happens is excessive cranking when starting the engine after it is warm. As I said this is really rare and I'm guessing is unrelated but the more info the better.

Anyone know what sort of paramaters or conditions need to happen to make the light stay on? I've noticed it is supposed to come on when you turn the key "on". The split second you start cranking, the light should go off. What exactly is that light an indication of?

I'll even put some Ferrari bashing in here. Since Gerber has the car, I pulled my 328GTB out of hibernation. What a turd! At least when compared to the 964. Rides like a truck, wallows around, no power steering, etc. Still looks and sounds pretty good, though. I guess the fact that I never drive the thing after getting the 964 says it all.

Still looking for suggestions if anyone has some. We just plugged in a known good RS America ECU and so far no problems but we'll see... I'm not convinced.

 

The most common problem for 964s, and as described herein, is problem with
the ignition system:

1. bad ignition wires or very oily
2. bad spark plugs
3. bad spark plug connectors, mis-aligned, or oily
4. bad distributor caps & rotors
5. bad ignition coil