I have to say my car feels fantastic after the update. I've driven about 50 miles so far and it has been hiccup/stumble free. Even did some slow acceleration tests through the 2-3K RPM range in 5th/6th/7th gear and it was very smooth. The shifts have really smoothed out as well.... most of the time I could not even feel them at all.

All my driving today was in sport/automatic PDK mode.

Will update after I rack up more miles tomorrow.

The invoice said that I receive the WF86 DME Reprogram.

 

Nice! Keep the updates coming - we know that sometimes after any DME refresh it can feel great for a few days but then go back into stumble mode.

 

shhhhhhhh think happy thoughts.

 

Happy thoughts. Happy thoughts. The folks in Zuffenhausen have finally listened to us and have issued a software update that fixes all our problems.

 

I went to my dealer yesterday and they do not have this reprogram notice. Is it specifically for certain models or what?

 

The car doesn't make it to the dealer very often so called Friday and had them run my VIN to see if there was any outstanding service actions needed. I believe my car is an early 2013.

 

I'm really seeing a correlation with my stumble and the weather - specifically, the humidity. I've noticed on nice, clear, cool days (60 deg F no humidity) the stumble is less apparent. Then yesterday morning it was rainy on my way into work and the stumble was worse than usual.

In my mind this all points to faulty sensors.

 

^^^^Very interesting observation. It very well could be some sensor(s)...

 

I've started making inquiries into local independent shops to see if they could just give me a second opinion on this matter. It's gotten to the point where it's bothersome enough that I need to have someone who's not me and not the dealer tell me "yes, indeed, that's some rough acceleration and stumbling you got there".

 

I've had the stumble since the beginning. I took my car to the dealer a few weeks ago for the annual oil change, brake flush, etc. and asked them to check for any S/W updates. There were many. I was mostly interested in the DME update being discussed here, and it was available for my car.

After installation, I can conclusively say that my problem is 75% eliminated. The other 25% I can still lightly feel the stumbling effect, but it has greatly diminished. It seems that the update moved the RPM range for my issue from the broad range of 2K - 3K down to about 2.2k thru 2.6K. Even then, when its there, it's not as severe as before. I have noticed that when the engine is cold and I happen to change from 1st to 2nd when it enters that range, it bucks and jumps a little. But, it did this in the broader range before as well. After it's warmed up, it settles down.

The reason I know it's improved is this: Driving it a couple of days ago with the stereo turned up loud, I realized that I was moving along with the car still in 3rd gear with the RPM's gradually increasing within the original broad stumbling range, and it was running very smoothly.

In summary, let me say that this has improved my car greatly. Is it possible that the DME may adjust something through adaptations that will bring the stumbling back? I guess only time will tell.

One thing did change on my car. The PDK tranny seems to change gears a lot harder now than it did before. In Normal mode, sometimes during the changes between 1st, 2nd, and 3rd, it really changes hard. It feels almost like it's in Sport or Sport+ mode and the electronic engine mounts are activated. I mentioned this to the dealer, but they didn't have any answers. Anyone else experiencing this change?

 

A lot of us have had DME re-flashes which alleviates the problem for a few days, but it always seems to fall back into stumble mode. It's like it's a sensor or faulty feedback causing some "learning" in the system, which then exhibits the stumbling.

Please update us in a few days!

 

Read to the tune of John Lennon's "Imagine"

Imagine all Porsh dealers
Caring bout their clients
It seems very unlikely
Cause they don't give a damn
They're just sell-ing cars, without a worr-y in the world

Image all Porsh dealers
How many cars they'd sell
If they only care bout clients
And bout the damn-ed stumble
They'd sell lots more cars, over the long run

 

Talked with a local independent Porsche mechanic on the phone today, and off the top of his head he said his first thoughts were the throttle body or carbon buildup on the intake valves. I'll be swinging by his shop next week so he can take a ride and see what the next diagnostic action would be.

I know I've read here about throttle body replacement having no effect, so what about carbon buildup in the intake? With DFI you don't get the fuel washing over the backside of the valves.

 

I doubt that there would be significant enough carbon buildup after just 2-4k miles.
As for the throttle body, I can categorically say that its replacement on another stumbling 991 did not resolve the issue.

But at this point you have nothing to lose by having it diagnosed by an actual mechanic..

 

Has anyone tried the Cobb flash?

ChuckJ