I’ve got a very intermittent (half a dozen times in the past year) stalling problem that I’d like to run by you folks.

It’s a 2010 997.2S cabrio, and every so often it’ll stall out when the car’s coming off throttle. To give you a scenario, the last time it happened I was at a stoplight. The light turned green. I accelerated not fast, but ‘peppy’ like I always do, and the next light in front of me turned yellow so I put the clutch in to brake and slow down and the engine died.

Time few times before that were under similar circumstances. It’s always when I’m coming off throttle. It’s never stalled out while idling, or cruising, and it’s never taken more than a second of cranking to get the engine started. The scariest time it's stalled was in mid turn, because I lose power steering and power brakes. That adds some excitement to the trip.

I’ve discovered that I can put it into the appropriate gear while I’m in motion and pop the clutch to get it restarted. This is much more preferable than having to come to a stop in traffic, take the key out, put it back in and crank the engine.

Things I’ve tried so far:
- New air filter
- New MAF
- Cleaned throttle body
I’ve taken it to the dealer right after a stalling episode and they can’t find any codes at all.

They tell me that when it was new, it received the updated HPFP from the service bulletin in 2010. I’ve read up on how the car behaves when the HPFP is bad (long crank time, sluggish speed) and it doesn’t seem like that’s my symptoms.

Any help is appreciated!

EDIT: One thing I wanted to add is that this has never happened when the engine's up to full operating temperature. It's only ever happened when the engine was cold (in its first few minutes of running in the morning) or warm (being restarted after an hour of sitting in a parking lot).

 

Reads like an intermittent fuel supply problem.

With the updated HPFP you are not out of the woods.

My tech sources told me a while back -- I forget just how exactly this subject came up -- but they told me a while back that in some cases the early "updated" HPFP acts up and has to be replaced again.

I don't recall, if I ever knew, the symptoms that would prompt replacing the early updated HPFP but I could believe the behavior you describe could be such behavior.

Another possible explanation is the crankshaft position sensor is loose or flakey.

In either case I'm not sure how one would go about pinpointing the cause of the problem. Replacing either the HPFP (again) or the crankshaft position sensor are not inexpensive jobs, though the CPS job would of the two be the least expensive one, one you might be able to do yourself if you are a skilled DIY'er.

 

Thanks for the help, Macster.

My hunch was the MAF, just because in my 996, every drivability problem seemed to point back to the MAF. That's not the case here.

The tech at my dealership also mentioned the Crank Position Sensor, so the fact that you bring it up, too, interests me. I found some old threads where people had symptoms similar to mine as well, and it turned out to be the CPS.

I see that I can buy one at Autozone for $75, and it seems relatively accessable from under the car. Do you happen to know if it's a simple swap, or do you have to worry about 'air gap' and sensor adjustment? I'm willing to throw that part at the problem first to see if it helps (if I'm not in danger of ruining the car!).


Thanks!

 

Just throwing out another idea. I had this issue in my C4s and it was simply the gas that I had recently put in the tank had a lot of water content. This typically happens when you fill up at a gas station with a car wash. Anyways, I added a bottle of HEET to the tank and it fixed it immediately.