Perhaps the issue is with the software interacting with the air mass sensor readings or something like that. The plenum change would definitely affect the readings one way or another...

 

The plenum will probably not work. I got he retrofit power kit that comes with a new plenum. My car did NOT have the stumble issue before or since, just because you have the power kit doesn't fix the problem. Matt (Money2536) got his original 991 with a power kit and started having issues at about 4000miles. That's why he jumped up to the GT3. So I am wary of a new plenum fixing the issue solely. But if it worked for the other user, then more power to him, pun intended!

 

The thing about the PK is that it also comes with a different set of cams. In doing so, the fuel/air ratio would probably remain the same except more in volume which might explain why the kit doesn't resolve the problem.

When I first got the car, it did not stumble. All I wanted was more power and the PK is not an option for me here in China due to emissions. My only choice was IPD so I ordered the plenum and that's when the stumbling issue started.

It got to a point where I was going to sell, yes it was that bad so I placed an order for a Turbo S. At about the same time, the plenum arrived so why not? Already paid for it so got I it installed. After a day of driving for the ECU to adapt, bam!! no more stumbling. Its been 1000kms since the install and all is well, the enjoyment of driving this car is back.

I decided to keep her. Only issue I have now is the wife's complaining about another 911 (they all look the same to women) that I ordered. Don't know whats worse now, the stumbling or the wife's nagging!

 

That sounds hopeful. I'll have to start a discussion with my dealer.

I would really like to get "the love" back driving my car.

 

I wouldn't waste my time if I were you.
Aren't these are the same folks who refused to acknowledge that there's even an issue.

The mere suggestion that an aftermarket component may resolve your imaginary issue would clearly be bordering on blasphemy..

 

Ha! Good point, but I would just frame this discussion as me wanting the extra power. Because I just got a lowly 3.4 model. I need the extra horsepower in my daily commute.

 

Genius..

 

has anyone been able to capture this on video? maybe a post on youtube to show porsche what's going on could go a ways to a solution ...

 

Fairly sure that Porsche knows what's going on.

 

In most cases it's too subtle to show up anywhere but the seat of your pants. No abnormal indications on the tach. And trust me, after dealing with it for any length of time it becomes very noticeable and very aggravating.

The only way I've been able to document it is with a sound recording using an external mic mounted just above the exhaust. You can hear the distinct change in pitch as the rpm's go through approx. 2500.

https://www.dropbox.com/s/30myokhpkartro1/gp1.mp3?dl=0

 

That is the most accurate audio reproduction of the problem I've heard to date. Well done.

 

It's very subtle. You can't really even see it in the tach. It's very much a seat-of-the-pants feeling. I had a PCNA field tech show me a graph of engine systems on a similar car and there was so much going on with lifters, air flow, throttle position, fuel delivery, etc, that it's not surprising one little sensor or something out of whack would really mess up the end result - namely a smooth power delivery.

 

Any updates on the lack of stumbles with the IPD?

 

Its almost like the camshafts don't know if they want to advance or retard at 2600 rpms. But thats just me.

 

I have a class Action attorney friend, do you think this well is deep enough ?