JasonAndreas

The first warning in every Bosch electronics manual I've ever read is, "Never disconnect the battery when the engine is running". Your alternator won't like it very much and I'd imagine the unstable voltage levels wouldn't be the best thing for the various control units.

1999Porsche911

Upon disconnection of the negative cable, all circuits are open and no harm can come to them. Like when you blow the main fuse.

redduck996

ok, i've added the fuel cleaner and a new tank of gas.. That didn't seem to fix the problem. I'm skeptical about testing the car to see if it's an electrical problem or not by reomving the negative line on the battery.. I think i'll just take it to the shop..
So what are some causes of this engine run-on? Alternator, battery.. yadda yadda yadda..

1999Porsche911

ok, i've added the fuel cleaner and a new tank of gas.. That didn't seem to fix the problem. I'm skeptical about testing the car to see if it's an electrical problem or not by reomving the negative line on the battery.. I think i'll just take it to the shop..

What happens when you turn the key off? Does the electrical circuit all of a sudden open? Gee...I wonder what happens to the electrical circuit when the battery is disconnected????? But, if you're skeptical, take it in.

It is not the discontinuation of electricity that causes any dmage, it is the sudden appearance of it that may.

GabiOsz

You have to drive the car pretty hard for around 100 miles for the fuel system cleaner to start working and have maximum effect, have a really spirited drive on the weekend!

I can usually stop the car doing it if i rev it slightly before switching the engine off (only to about 1500 rpm).

It could be the electrics, give the battery thing a try too.

redduck996

Well, i took her in today and as I was describing the problem to the tech advisor a technician was standing there. he said that the noise is normal and that the flywheel makes that clanking sound after the engine cuts off because of heat and poor dampening. I told them to take a look at it anyway. I had them check out the wind noise and rattle from the 2 doors as well..
keeping my fingers crossed..

1999Porsche911

Well, if it is the flywheel then you should be able to at least determine where the general location of the noise is coming from. Put you head under the car when it is shut off and see if it's coming from the flywheel area. Then open the engine lid and do the same.

Keep us posted.

redduck996

Is the flywheel suppose to make that rattling/clanking sound when the motor shuts off?
I'm anxious to see what the dealership tells me it is..

1999Porsche911

If it does, then it is likely a bad flywheel. The rotation of the flywheel (dual Mass) would nee to be checked to see if it is within specs. It should rotate (twist) only about 1/2 inch (15 mm) to the left and 1/2 inch to the right and spring back to the start position. If it is outside this range, then it is bad.

redduck996

hmm bad flywheel, do you think that's covered under warranty or is that like wear+tear?

GabiOsz

Well, I hope you get it sorted.

The noise and symptoms you describe are the same as my 993's problem, except that mine is a Tiptronic and I don't think they have a fly wheel, isn't that part of the clutch mechanism?

redduck996

Just got my car back..All I can say is they did absolutely nothing..
First they said they tighten a few speaker screws on the right side (which was where the rattle was coming from) I still hear rattling from the door area.. It could be the passenger seat bc I do see it shake alot.
The driver side wind noise is still present. They said they adjusted the window by moving it up and out a smudge. I still hear drastic wind noise at 40-55 mph.. Not sure if thats normal or not
The rattling/clanking sound he said was from the flywheel which he said was absolutely normal. Odd thing was another c2 pulled into the garage area and as the guy shut off his engine, I didnt hear the noise I had.. So what should/can I do now, Turn up the radio and the noise will all go away?

What a waste of time taking it to the dealer..I thought they get paid for warranty work?

GabiOsz

Redduck996, I am not sure that the engine idleing after you switch off the igniton is the flywheel noise that is described, there are a couple of threads on this on the 993 board which relate to the Light Weight Flywheel that many of them fit to the cars making this noise, it dosen't sound the same, here is a link to one of the disscussions:

https://rennlist.com/forums/993-forum/179036-engine-shutdown-noise.html

Nick Crooks

I also had a 72 Chevy Nova as my first car - it dieseled endlessly. Very embarressing and caused me to park it far from any watching females.

redduck996

I'm not sure if it is in fact the flywheel, but the gentleman at the dealer said it was the flywheel and that it was normal. I don't think he really investigated the issue thoroughly.. I'm going to take it back again and demand for someone to look at it. I just want to know from my fellow P-car owners if this in fact is normal or do you guys hear nothing after shut off?