redduck996

I get this prolong engine idling for a second or two after i've already turned off the car. Do you guys experience this? It sounds like the car doesn't want to shut down for that split second even though i've turned the key..
With all my other vehicles,when I turn it off, it's off no hesitation. With the p-car it almost sounds like the car is choking.. Could it be a weak battery?

thanks in advance

houldsworth1

I don't get this. Totally WAG here but perhaps your mixture is over-rich - have you checked the spark plugs to see if they are blackend?

ArthurK

I had a similar thing on my 993 but I think it was more the ignition switch. I think it didnt "disconnect" when I had turned the key to the off position. When you turn the car off is the key out of the ignition and still going or is it just at the point of being in the off position and key still in? Try turning it further to the left and see if it makes a difference

Gnome

This used to happen on my '72 Chevy Nova (years ago). It was "dieseling." Someone else might know the technical factors behind this. Basically, it would keep turning over -- drawing fuel into the engine and then igniting it without a spark from the plugs through residual heat and pressure in the cylinders. I believe this is how diesel engines run -- they don't use spark plugs. I didn't think this was possible on a modern day car with fuel injection, electronic ignition, etc.

Brings back memories. That car could keep running for minutes after I got out and locked the door.

TT Surgeon

bad gas, timing, both

clum553946

What Gnome is refering to is "dieseling." Carbon deposits on the head or top of the cylinder heat up during engine run. When you shut the engine off, these deposits are red hot & can continue the combustion cycle albeit not very smoothly. I hope this isn't the case since this phenomenon can hurt your engine. It's very rare in newer cars, but did happen in older 60's & 70's autos. I think leaded gasoline had something to do with it but can't remember. Bad gas & off timing can contribute to this. You should have it check soon!

Mr. C4

or a bad ignition barrel!

GabiOsz

I have a similar problem with my 993, several people have similar problems with their 944's, some say a leaky/clogged fuel injector combined with residual heat in the engine (whether it be hot carbon deposits or the still hot spark plugs). Try a bottle of fuel system cleaner in a tank of petrol and give it a good hard run of 100miles or so, this helped my car for about a year, but recently I have been getting it again, although intermittantly. I know the cars are different, but I hope this is of some use to you.

Here is my thread on the subject: https://rennlist.com/forums/showthre...ight=dieseling

redduck996

Noooo, are you guys saying my car is "Christine" reincarnated?.. It doesn't run on its own for minutes at a time... It's only like a second or two.. I'll try the fuel cleaner stuff.. I heard that wasn't good for the car hmmmm. Maybe i'll have the dealer take a looksy.

GabiOsz

No my car dosen't run for minutes either, they are fuel injected so won't do that once the DME has stopped pumping fuel, unless you have a leaky injector or something. Steve Wiener one of the Rennlist specialists suggested the fuel system cleaner to me, so it can't be that bad.

redduck996

I'll try that... you mean fuel injector cleaner? Any suggestions as to which brand?

Mr. C4

Muligan,

As I said, there can be a short in the ignition barrel so even if you have turned the key anti clockwise all the way, power is still getting through. 996 and 986 are notorious for malfunctioning ignition barrels.

Ciao,

Johannes E.

redduck996

I guess it's time to take her in again.. at least I get a free loaner

GabiOsz

I was recommended "ventil sauber and techron" but I don't get that in the UK so can't comment on its effectiveness. The ignition barrel could be the culprit, but I would try the additives first as a cheaper alternative, if it dosen't help work your way up the expense table, my mechanic has no idea so I am working through the possibilities starting with the cheapest option

Let us know how you get on, I am having my O2 sensor changed this week to see if that helps.

1999Porsche911

To isolate whether it is in the electrical system or not, while at idle, disconnect the negative battery able and see if the car dies immediatly. If it does, look at the electrical system...if it does not (shuts down with the same problem you have now), then it is not the electrical system.