Jay-S

I've stalled my car (991 4S with PDK) a few times in auto stop-start. It tries to restart and basically fails. No big deal. Just restart the car and move on.

I've now had my car stall twice in the last two months and it was quite different.

1. Sitting at a light, auto stop-start stalled on reignition but was now accompanied by multiple error messages (fault all wheel drive system, PCM shut down, Sport mode disabled, auto stop-start disabled). Once I restarted the faults cleared and I was on my way.

2. Sitting at a light, auto stop-start OFF the RPM's became highly erratic and it felt like it was trying to stall. I slipped it into neutral to see if giving it some gas would help. It did not so I put it back into D and it promptly stalled. Multiple error messages (fault all wheel drive system, PCM shut down, Sport mode disabled, auto stop-start disabled). Once I restarted the RPM's were erratic again and it tried to stall. Green light and I just hit the gas. The car returned to normal. The faults cleared after I restarted at the light.

In both cases, car was fully warm. I use Chevron gas so am thinking bad gas is not to blame.

Car is at the dealer now but I suspect they will have nothing to go on. They indicated warning messages can happen after a stall.

Anyone have anything like this happen to them?

Augustomf

NO. But stalling, erractic RPM could be the following:
1: Bad Gas, but for bad gas you would also feel the car's performance drop considerably, specially under load and have knock issues.
2: Vacuum leaks, but they would have to be severe
3: My bet for your problem, bad ignition coil. It can happen even on a new car, or poorly mounted coil, or water got there etc. You would get erractic idle, and could diminish at higher RPM. Dealer will read codes, see if there was a miss-fire and replace the coil and plug.

Let us know what dealers says.

chuck911

The 991 uses multiple ignition coils. If one were bad it would run rough but not to the point of stalling. For several to be bad almost defies the odds. More likely its the downside of these care getting so technologically complex. Some are seeing slow low-rpm responsiveness with PDK. Some episodes of unexplained twitchy highway handling. Batteries drained dead for no apparent reason. Stalling. Cars that just won't start. A common theme, software glitches. Likely dealer response? "Uh, we dunno." Meanwhile, the vast majority are thinking huh, mines never had any of those problems. Until they do.

Augustomf

Agree.

My 2c is on coils because I had the same problem on my wife's 535ixt. Two coils went dead, the car stalled, knocked, idle ruff, went into limp mode.
The problem with these coils is that if even one goes bad, the car missfires and the software begind to compensate, and in our case put the car into limp mode, which allowed my wife to crawl home.

mtony

Could be the infamous crankshaft (or is it camshaft?) position sensor failure.

Dyim

How erratic are you talking about?

I found my C2S's idle does fluctuate a bit but I would never think it would stall and it never did. I do occasionally feel a slight vibration thru the seat. I figured this engine will never idle as smooth as a Lexus, for example.

FWIW, I have never enabled the start stop function. Maybe try turning it off and see what happens?

Jay-S

It was swinging several hundred RPM if I'm remembering my tach right. Not like when it normally moves around at idle 30-60 rpm. It was like the car was possessed.

FYI -Auto stop start was disabled the last time.

Dealer was backed up on Friday so hopefully I'll find out Monday or Tuesday. In other news I like the Cayenne diesel loaner.

Dyim

So you mean it would fluctuate between 1500 to 1800, for example.

Keep us posted.

MarcusG

When things like this happen your smartphone video camera is your friend. That way the service dept. will believe you when you hit playback.

Jay-S

Just got my car back (farewell Cayenne diesel!). They picked up misfires codes on one cylinder bank (CYL 1, 2, & 3). They were concerned about spark plugs and/or ignition coils but everything checked out. Best guess is bad gas or a little water got in. Where the water got "in" I'm not sure.

I did some homework and found that the last occurrence - the only time a stall was not associated with Auto Stop Start (can't really abbreviate that can you?) - I put gas in from a different station that day. Was a Shell station though so should have been fine. Service department indicated if the station's tank was just filled it is possible the fill stirred up enough junk to cause trouble. No idea if there is any truth there.

So...no real answers but at least the misfires registered so I'm not totally crazy. We'll see.

Jay-S

Oh...and my BlackBerry's quick key is now set to video

rpilot

Yes you can. Add Porsche in front of it. PASS

Jay-S

Ah, yes. Adding Porsche to anything makes it better

Augustomf

That was one of my options, but did you feel any of the other symptoms I mentioned you should have with bad gas? Bad performance, hesitation under load, severe knocking?

Did they empty your tank and put new gas in???

Jay-S

Bad performance: Just higher RPM variation at idle than I was accustomed to.

Hesitation under load: Not that I could tell.

Severe knocking: I believe there was knocking. It's been over 20 years since I've been in a car that elicited that particular sound and it didn't register at the time. When I read your post, I was like, "THAT'S what it was!"

Empty tank and put in new: they did not

It's had new gas for about a week. No knocking. The RPM's at idle are more steady.