Thread status: Derailed by people who think the issue in question has something to do with the PDK.

 

Sorry about that, I don't want this to be that type of discussion. Just my actual experience with this issue and just hope that my opinion helps, if not then I apologize for bringing this up. I hope you all get this issue solve, or Porsche get this issue fix.

 

I've got a may 2014 build C2S 7MT. Did euro delivery in July and never noticed any stumbling issues. I followed the "euro break in" procedure, which according to the factory handover guy Louis was "no sustained driving over 5500 rpm until 2000km. Then you are ok to do whatever."

I did notice that at 3000rpm and 5000rpm there was some sort of cam change at full throttle. Felt like some lumps or peaks in the power delivery. It seemed normal enough to me. Then upon taking delivery in the US and reading through the threads on the issue I was able to get some minor intermittent stumbling around 2600rpm with part throttle. However I've never had the "fishing line" phenomenon or the steady stumble from 2000 to 3000.

So far the even with this minor and infrequent stumbling it doesn't seem to bother me. It seems more or less like a normal engine doing its thing.

I also have a 2003 BMW M3 that I've had since new (also an ED). It has always made a gnarly clunk when engaging the clutch at low speeds (such as pulling into driveway). Back in the day, The folks on roadfly.org complained bitterly about this much like we are doing on the stumble issue. BMW also considered this to be the normal sounds of a "sporty car". Their words. I've also had delays in throttle response due to the Vanos on this car as well as peaks and dips in the power delivery. I just assumed this was normal and have lived with it for the last 11 years.

I'm of the opinion that the stumble issue is just part of the various cam plus trying to quickly go between high mpg and high power modes. Also, doesn't it "learn" your driving style. Perhaps some people have a driving style that exacerbates this change over and causes the cam mapping to hunt around?

This could also explain why the problem resurfaces after the software is reset. Maybe it's re-learning the owners style of driving and as a result setting the change over point after a few days of driving.

Also, I have been blending sunoco 100 octane with California 91 to get 93+. In Europe I was filling up with super plus at 98RON and sometimes shell 100RON. I've never run a full tank of plain 91.

Just my thoughts.

 

I have a 50th with 7MT and it does not have the stumble issue, thank goodness, and hopefully it never appears.
I have read this thread over again, and read the 6-Speed Online thread including the two sub-threads with the polls. This issue makes me worried!
My question is regarding tracking your car - no one has mentioned whether tracking a car that stumbles causes any change in the behaviour. What I am getting at is the thought that if the car "learns" your driving style then what effect does a track day have on that learning process, and does it affect the stumble - clearly if a learn-mode-aggravated condition occurs, one would reasonably expect a track day to alter it.
I get that you wouldn't notice it while on the track - but what happens on the drive home afterwards, or during the next day or two?

 

^but I don't think the car has a learning mode for a manual trans. Does it? What would it need to learn??

 

AMEN!! The voice of reason speaks.

@Hugh Jardon - The fishing line tug happens when cruising. The stumble / fuel starvation issue occurs when accelerating and is quite different from the variocam dip ~3000rpm.

 

I see. Well, I haven't noticed anything like the fishing line or bucking thing when cruising. Other than some minor intermittent non-linearity during partial throttle acceleration from time to time I don't seem to have developed this issue to the extent that some have. I've only got 2400 mi on the odo at this point.

I suppose it could just be a matter of time before it does though. I'll keep an eye on it.

Of course if PCNA suddenly issues a software re-program and it fixes everyone's issue then we will know the deal was.

 

My question wan't specifically directed at 7MT.
Has anyone (MT or PDK) with the stumble issue tracked their car? If you have, has it altered the problem in any way, for better or for worse, temporary or otherwise?
Has anyone who tracks their car had a problem with the stumbling?

 

I have a bit over 5000 miles on my car since it's 12/2013 delivery. I have had three track weekends thus far and no stumbling issues.

 

7mt tracked regularly slight stumble from day one no change.