Great, now I got it too! ‘16 C2S Cab, PDK, just turned 9K miles. Mine is a similar complaint. I would describe it like rpm/motor surges back and forth about 100 rpm., up and down under steady driving/cruising trying to just maintain highway speed, like on-off-on-off-on-off. Coming back from a local P-car rally Saturday, my wife noticed it from the passenger seat. She thought I was doing it intentionally.

I have an appointment with the service dept next Tuesday. While making the appointment, I asked the scheduler if he had ever heard of my problem before. He said no, it’s probably normal for the car! Deliver me!

I can’t wait for this “Porsche experience.”

Well, here goes.

I met with the local P dealer service dept yesterday and explained my stumble situation. The service writer and tech denied ever hearing about this problem. I explained to them that it has existed in large frequency since at least 2013 as documented on the net forums and in Porsche own records as scores of owners have complained. Both the service writer and the tech were stoic faced.

I took the tech for a test ride. Naturally, my car decided not to cooperate such that when we hit an incline on the highway there was indeed a “fish tugging on the line”, however that fish was just a baby. We did notice movement on the tach of approx 50 rpm up and down and the corresponding slight audio/exhaust increase-decrease. I could feel the on-off-on-off of the stumble very slightly. The tech denied feeling it.

While I would point out when it was happening (several runs up and down a stretch of highway that included a bit of an incline), the tech would proclaim that this is more audible and visual on the tach but not something he could “really” feel. At one point he admitted the he could feel it ever so slightly, but then tried to double back on his words. It seemed to me that he didn’t want to admit that he could feel the stumble.

Since I am no mechanic and couldn’t locate the megafalator switch even if you pointed at it, the tech tried to tell me in plain English that the car was “bogging down”. That prompted me to ask how do I bog down an automatic trans ( I know, PDK, but bear with me ), without purposely shifting up when the car calls for a lower gear? He said, the car was bogging down. He said, “It’s not a luxury car; it’s made to be driven hard on the track then driven home. “ So I agreed and said this sounds like a defect in the car so please fix it so it won’t bog down.

The tech continued to revert to his original statement saying that the car is vacillating by trying to go faster and and then trying to hold back for economy. He continued to say that since it’s mostly on the tach and he really can’t feel if, it’s really not broken such that it can be repaired.

He didn’t want to “open a ticket” which I understood to mean entering a formal complaint into “the system”. I asked him to open ticket on this. He said Porsche will require a test on the gasoline in the tank. I suggested in order to save time, set his tester to recognize Mobil Synergy 93 Octane.

I asked him what could be done. I asked if this was a plenum issue, a valve issue or throttle body issue. I asked if it was a mechanical issue. He said no to all. I asked it it was a software issue. He said no. He also said my car threw no codes, and there were no updates to be added.

I asked what could be done. He said he would perform a reset by way of forced adaption/transmission adaption. I understood that to mean resetting /reloading the software back to “factory setting”, as he explained, “so the transmission can ‘relearn’ how you drive.” In effect, reinstall the operating software to a setting when the car was originally received. He said this would change the “kiss points” (I started to get nervous).

After about 45 minutes he appeared with my car, having completed the factory setting installation. We took a ride over the “test”track. This time he was driving. He explained that the car was shifting differently, in effect, trying to “learn” As we got to the incline and rpms were near 2K, I felt the “fish on the line” pull, give and take similar to our earlier run and looked over to the tach wavering 50+/- rpm. I asked can’t you feel that? Silence.

I left the car at the dealership and asked him to continue working on the problem. I asked that he take the car out again to see if he could tell if it was stumbling.

Later that afternoon I got a call from the service manager. The s/m also took my car out on the “test loop”. At first he said he definitely knew what I was talking about and that he felt it. I was excited because he actually admitted it. He said in the past he had other similar complaints from several other clients who then dismissed their own complaints as not being important enough to pursue, as if they were just mentioning it in passing. Thus, he never had cause to look into the problem.

When I asked is my issue a mechanical issue or a software issue, the s/m replied, “That’s thing of it. I don’t know if it is actually an issue. I can feel what your talking about, and before I commit to saying it is a problem I’d like the car for a couple of days.” Another admission that he actually felt it.

When I asked if he could feel the hesitation, he said, “I don’t feel it as a hesitation, I feel it’s just ...I hate to say it but it’s almost like it’s unsure of what it wants to do. It’s right on the threshold where it doesn’t need to downshift to 6th gear so it’s adjusting valve timing and valve lift to compensate rather than shift up.” I thought, bingo! Go to the head of the class.

The long and the short of it is he agreed to contact Porsche and get back to me when they do. At the end of the conversation, though, he back tracked and said, “...like I said I didn’t fell anything and I was looking at the tach and saw the tach changing and moving a little bit. I did not drive the car prior to XxxX reflashing the PDK so maybe it changed something I don’t know.”

In effect he initially confirmed he felt the stumble, but at the end of the conversation, reversed himself as if trying to protect Porsche or the dealership. (To be clear, I didn’t purchase this car at that dealership.)

The car now sits at the dealership, as I sit waiting word on what is next, which no doubt will be nothing.

I read the epic thread on 6Speed last night. Some of you guys have gone through this horse dung for 4-5 years. My car is 3 years old. I had it built over the summer of ‘15 and received it in late August ‘15. Thought I’d get the last of the 3.8 NAs. My wife, God love her, said dump it and we’ll get another one. What a gal! But I just can’t. It’s too new to sell/trade. I’d take a bath with depreciation.

So, we’ll see what happens. I’ll post the results.

p.s. Stealth, thanks for the welcome to the support group. Don’t know that I’ll be much help.

NDD

Wait does it to it if you just put it in manual mode and drive with the paddles?

I’ve found “automatic” mode to be worthless so I never use it.

Weird like I’ve said before, mine stumbled hard when the throttle body was giving out but since then no stumble and I have 83k miles on it now.

i have not really explored any combinations of driving modes. I will extensively when I get my car back. The stumble has only occurred while granny driving on the highway, trying to bring speed up from say mid 60’s to mid 70’ smoothly without the trans downshifting.

Around town, I agree, automatic mode is boring. I’m typically in Sport and working the paddles. I never noticed the stumble around town.

There may be some weather/heat/humidity effect at play. I notice the most sever stumble after a 4-5 hour rally on a unusually hot and humid afternoon. The week before, on the highway in the warm evening (but not nearly as warm or humid as the rally day) I got my first sip of stumble fluctuation. It was almost imperceptible until I started watching the tach. Not sure if heat, heat soak, or humidity, plays a part. By the way, my city is 200’ above sea level, so not starving for air.