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I hope this issue picks up steam here. The 6Speed thread on it is amazing. Unfortunately, 6Speed has turned into a graveyard over the past year. The only hope for discussion is on RL here.
To some of the guys who have been at it for years, it may take some catching up for some of the guys on RL. Be patient. Overall, the knowledge of some of the guys here is amazing.
I hope some answers can come soon for all involved.
That would be nice. Hopefully we can keep this thread on point. I'll do my best to ignore the haters :-).
I've been dealing with this problem for over two years. I have been to my local dealer 4 times about this problem. Last visit I had a visit with the regional PCNA tech. He let me drive first then he drove. He told me that the stumbling was "normal". He then showed me a chart of all the various changes going on - it was a log from an owner's car that was having similar issues. Throttle position, cam position, air flow, etc. He basically tried to tell me that I was just hitting a spot where too much was trying to change to be able to provide smooth acceleration. But that's bull**** if most of the other cars can accelerate and drive smoothly. If it really were "normal" then every car should do it. The VarioCam Plus transition at 2800-ish, sure, but not the more general stumbling before that.
I've has tried it with PSE on and off. No difference.
The fault exists with both Base and S models.
It is definitely not the vario-cam blip at 3000rpm.
This occurs before that and feels just like when we used to have a vacuum line issue in the old days.
Also note, when the DME is reset or the battery is disconnected overnight, the problem goes away. But once you drive the car again for a couple of hours the stumble returns.
So the DME is compensating or trying to correct something...
I think that suggests that the "learning" mode of the DME is in part responsible for this... if a "clean" DME does not exhibit this behavior but after some time it does, its clearly monitoring
some parameters and mis-tuning the system such that it exhibits this behavior subsequently ...
I'd be tempted to suggest going to a track day, reseting the DME (battery disconnect) and drive it on track for the day ... see if the problem returns?
That would be nice. Hopefully we can keep this thread on point. I'll do my best to ignore the haters :-).
I've been dealing with this problem for over two years. I have been to my local dealer 4 times about this problem. Last visit I had a visit with the regional PCNA tech. He let me drive first then he drove. He told me that the stumbling was "normal". He then showed me a chart of all the various changes going on - it was a log from an owner's car that was having similar issues. Throttle position, cam position, air flow, etc. He basically tried to tell me that I was just hitting a spot where too much was trying to change to be able to provide smooth acceleration. But that's bull**** if most of the other cars can accelerate and drive smoothly. If it really were "normal" then every car should do it. The VarioCam Plus transition at 2800-ish, sure, but not the more general stumbling before that.
its a shame the PCNA rep didnt also compare to a car that did not exhibit such behavior to prove that it was "normal"
I'd be tempted to suggest going to a track day, reseting the DME (battery disconnect) and drive it on track for the day ... see if the problem returns?
Unfortunately this was also tried this with no difference whatsoever.
It is definitely compensating for something not being quite right.
But with their threshold parameters being set so wide apart, it seems that they've managed to avoid any fault codes from being generated.
Forgot to mention that when cruising at ~2600rpm on a slight incline (with or without cruise control), the tugging starts. This sensation almost feels like fuel or O2 starvation.
Another owner has had his throttle position sensor replaced and it made no difference, so a faulty TPS has been ruled out..
On an incline? Could this be related to accelerometers in the car sensing the incline?
I think one thing to do is to compile a video evidence reel of as many engine stumbles of different cars as possible and do what that Nick guy did - make it go viral on social media. It is the only language that PCNA understands nowadays...
You are part of the reason I stopped posting about it. This doesn't help me, or anyone else with this problem. Please stop. I'm not going to redline it in my neighborhood at 6am while leaving for work.
Surprise, surprise. There is driving to be done below 3000 RPM. It's not weak torque that I feel. You obviously do not have the issue.
I would love to know how you never let your RPMs drop below 3000. Please explain. Do you drop your clutch at every green light?
After rereading my post, I agree it was unhelpful, unwarranted and poorly considered. Apologies and hopefully you do find a solution.
Are we seeing this prevalence with 2015 and 2016??
What about a pattern with GTS cars?
My thought is, if bad DME's, and the fact that PowerKit cars might exhibit this less (GTS are PowerKit cars) and knowing PoweKit cars have a different DME.......it might be linked?????????
Are we seeing this prevalence with 2015 and 2016??
What about a pattern with GTS cars?
My thought is, if bad DME's, and the fact that PowerKit cars might exhibit this less (GTS are PowerKit cars) and knowing PoweKit cars have a different DME.......it might be linked?????????
That was also my thinking at one point, but what exactly constitutes a bad DME and wouldn't it throw an almighty code?
BUT the fact that the problem comes back shortly after a DME reset, does raise a small flag.
Btw, I requested the original factory delivery flash from PCNA - this request was also refused.
The prevalence is mainly in 12-14 cars due to the fact that when the poll was conducted there were very few 15's on the road and certainly no 16's.
To date I haven't heard of a single GTS with this issue.
The PIWIS needs to be connected to the car's DME and taken for an extensive test drive with the technician in the car until the problem manifests. Throughout the drive cycle live data monitors need to be observed. The scan tool is capable of live recording. After the symptom occurred you stop the recording and rewind the data to study it from the moment the fault has occurred.
My total guess at this point is that I would pay very close attention to fuel pressure at the moment the fault is occurring. I would look at the in tank fuel pump pressure and at the high pressure fuel pump. I believe the PIWIS is capable of displaying those pressures separately. If not,a mechanical fuel pressure gauge needs to be installed,but I doubt that's necessary on a 2013-14 model.
I would also take a very close look at the upstream oxygen sensors on both banks. In closed loop during part throttle they should go rich observing the extra fuel. If they go lean,it might indicate there's a fuel pressure problem,but for a brief moment and not enough to set a check engine light.
One thing to note : if the condition is occurring briefly and can't be associated with a malfunctioning part,there's a possibility it can be corrected through a software update,by changing parameters in the fuel map.
That was also my thinking at one point, but what exactly constitutes a bad DME and wouldn't it throw an almighty code?
BUT the fact that the problem comes back shortly after a DME reset, does raise a small flag.
Btw, I requested the original factory delivery flash from PCNA - this request was also refused.
The prevalence is mainly in 12-14 cars due to the fact that when the poll was conducted there were very few 15's on the road and certainly no 16's.
To date I haven't heard of a single GTS with this issue.
I think it is less to do with a BAD DME (some h/w fault) and probably either
an issue with certain versions of the DME learning s/w and/or some interaction
with some of the sensors on the effected cars.
Certainly a flash with the latest s/w might be a resolution.
I still think that given that a DME reset clears this temporarily it could be
related to how the DME learns from the car and adjusts the various
parameters accordingly.
Has anyone tried reseting the DME then driving the car *REALLY* hard in
sport or sport+ mode (and maybe even manual for PDK cars) to see if
there is any different behavior?
I think it is less to do with a BAD DME (some h/w fault) and probably either
an issue with certain versions of the DME learning s/w and/or some interaction
with some of the sensors on the effected cars.
Certainly a flash with the latest s/w might be a resolution.
I still think that given that a DME reset clears this temporarily it could be
related to how the DME learns from the car and adjusts the various
parameters accordingly.
Has anyone tried reseting the DME then driving the car *REALLY* hard in
sport or sport+ mode (and maybe even manual for PDK cars) to see if
there is any different behavior?
Yes, I did this and pretty much drove like an idiot (redlined) to see what would happen with the learning. With a 7sp MT C2S, this approach didn't make a difference.
There was also an instance were PCNA installed a data logger only to determine that the driver was "taking his foot off the accelerator", causing the stumble. (YES - at the exact same spot every time). This was their deduction even though the stumble could be replicated using cruise control.
Folks, PCNA is NOT willing to help resolve or acknowledge this issue.
Grass roots solution or bust...
Multiple DME flash / updates have yielded no improvements.
It is difficult to comprehend or appreciate how much time and effort has gone into finding a solution to this problem that appeared out of left field.
And why would anyone trade and buy another 991, only for this feature to possibly appear again??
If anyone in the S. Calif area (O.C. preferably) wants to experience the stumble first hand, shoot me a pm. Once you've felt it you'll understand why so many of us are desperately searching for a solution.
12-03-2015, 12:57 PM
