Bluey

I’m trying to get to the point of accepting that my 991.1 C2 with 99,000 miles has a stumble, but I’m concerned that if I keep driving it this way it will eventually result in the failure of something in the engine or PDK.

Has the community reached a conclusion on whether or not the stumble is ultimately detrimental or can I just drive it carefree?

duxsi

According to Porsche it's normal and "operating as intended".

SilverSFR

Does your stumble cause a CEL or error code? A misfire/stumble will throw a CEL. Have you changed your plugs every 4 years or coils at least sometime in your 100K miles? 991 stumble when cold is quite normal. should go away once warmed up a bit though. Any modifications to said 991 that we should be aware of?

pfan

11 years of stumbling here with no known additional issues. Possibly detrimental to the mental health of the owner, but I think most of us have found that the car is just too damn good to let it spoil the fun.

chuckbdc

Nary a stumble in my launch edition 2012.5 991 C2S.

Bluey

No error codes at all. Dealer said they had it on the computer and saw no misfires, etc in realtime even though they could feel the jittery acceleration. They suggested a PDK two-fluid flush and reset, but I haven’t done it yet.

No mods to the car. Stock 2016 991.1 with PSE.

Yes, I have kept up the service with none missed.

Bluey

Definitely detrimental to my mental health! 😂 Glad to hear you’re driving carefree though.

pfan

If you do a deep dive into the stumble, you'll find that owners have replaced almost every conceivable engine part, to include plugs, coils, camshaft position sensors, O2 sensors, throttle bodies, oil caps ......... the list goes on and on. Interestingly, many of these replacements offer a short term fix, only to have the stumble return in short order. The DME/ECU apparently has a bug which will, over time, revert to the stumble condition.

Bluey

Aye, I’ve read all of that and I’m blown away with how much people have done and it’s not fixed it. Also can’t believe Porsche doesn’t acknowledge it as a problem.

Hank Cohn

Out of curiosity, has anyone with the stumble tried a tune and if so, was there an improvement? Is the stumble from the engine (assume so given the list of replacements) or PDK trans?

Thank you,
Hank

Bluey

My understanding is that people with manual transmissions also have the stumble.

SilverSFR

Manual 2014 C2S and no stumble for me.

vanlieremead

I have no idea what a stumble even is. I assume that while under some kind of acceleration, the car stops accelerating and then accelerates again? For my part, I have never had such a condition either cold or warm. In SC normal mode, the car is a bit anemic but is Sport is it never anemic.

tiiger

yeah, a good description of the stumble would be helpful.

I was assuming we're talking about when the car is at idle, and the little burble (and minute drop in RPM) every five or 10 seconds or so.

Tier1Terrier

Is this a .1 thing only or does it also happen with the .2 gen?