LSR

Apologies if there's another thread on this issue - I searched and could not find something on point.

I have a 2013 991.1 C2S with 18.5k miles. It's been maintained by the book every year, including new plugs and serpentine belt (based on age of the car, not mileage). The car's always worked flawlessly and has been a joy to drive. Zero complaints for all the years I've owned it. Recently, though, I've noticed the car hesitates and stumbles when I accelerate from a dead stop (e.g., from a traffic light) particularly in normal mode but also, though less noticeably, in sport mode (it's got Sport Chrono). Has anyone experienced this type of behavior and, if so, know the cause and cure? The car's due for its next yearly service in less than 3 weeks and rather than letting the shop go hog-wild (mis)diagnosing it, if I can steer the shop in the likely direction that would be great. Thanks in advance for your insights.

Porsche_nuts

known issue that has been discussed for years

lots of guesses as to cause, but unfortunately no solution

https://rennlist.com/forums/991/1207...esitation.html

LSR

Thanks for the lead. Bummer there’s no known cause or solution. Guess I’ll just have to ask my dealer about it. My guess is he’ll say “normal,” which l know it isn’t because it just started, but that will be that unless my local Indy has an idea.

One N Done

I had it with my old 2014 S as well. I have posted on it....dangerous at times if I was in auto mode. Loved everything about that car except that issue. Most of my driving with that car was sport manual (pdk) and I didnt have a big problem.

Good luck with your dealer/service.

SConn

I've had mine do it as well. What I started doing is driving a bit more aggressively. Start romping on it more often. It's worth a try and it's free. I did notice the PDK acting better afterwards.

Bemo

Same here, Sport+ or manual mode and higher RPMs make this go away. It's where the NA motor shines anyway!

SConn

Yup... Hit that kick down button on the throttle if you can. Super fun too!

Bemo

Agreed...the car begs to be driven aggressively. It's no fun in boring cruise mode, in fact quite annoying due to cabin noise. If you're on it, relatively within posted speed limits, it feels and acts like a sports car and all noises are welcomed.

A good cruiser it is NOT!

koala

I have adjusted my driving somewhat now that I really understand the parameters of reproducing the stumble. I used to be more conservative during the warm-up period, keeping the revs below 3k rpm. Now, I take it as high as 4k rpm so that I can stay away from that 2,200 rpm range.

LSR

What you say is interesting. Wonder if there's a clue here. Thanks to Covid-induced boredom, I've found myself driving much more aggressively of late. Several times a week I head to some twisties not far from my house, put the car in Sport + mode, and have some fun. The revs typically stay above 4k for quite a stretch of time - I might be driving like that for a half-hour. And it was only after I started doing this that I began to notice the car stumble as I drove away from a dead stop with the engine at idle. I rarely go easy on the throttle when I move out from a stop, and I haven't changed my habits in that regard. But before I started driving the car more aggressively, I had no stumble at all when leaving the line with the engine idling at 700 or 800 rpm. And now I do. Need to think about this - I know it's not the plugs, because they're brand new. Maybe the injectors? Or the gas? Back in the day, before electronic distributors and ignitions came along and it was easy to be a shade-tree mechanic, whenever my car started to stumble if correcting its tune didn't help I attributed the problem to bad gas. So I'd put in a can of dry gas with the next fill up and most of the time the stumbling problem went away. Though I feed my car 93 octane only, I wonder if adding a can of dry gas to the next fill up might help? Anyone ever do that? Or would that be bad medicine for a 911's engine?

koala

The other thread has touched on so many areas of speculation, but it is not believed to be related to injectors. Most people think it's a flaw in the variocam.

LSR

I don’t know why the idle stumble would be a variocam fault. The other thread talks about two problems - a hesitation between 2-3k rpm and a hesitation at drive off with the car at idle. I believe the variocam theory is discussed in the context of the 2-3k rpm stumble, not the idle issue. But I’m not sure if that. Whatever causes it, I’d like it to go away.

koala

Apologies, I missed the part about "idle" - my reading comprehension is at potato level today

SConn

Huh now that is interesting. Sorry if you've already said this, but have you tried driving it in manual mode to see if the problem still exists?

I started researching it about a month or so ago when I was going to romp on the throttle after I had to slow down for a car in front of me and was coasting. I put the pedal down fast after the car in front of me turned and my car just died on the water. Absolutely no response from it. It lasted so long, I actually took my foot off the throttle. In reality, probably 3 seconds.. Enough to go... Wth??

Anyway, since then I've been driving it much harder hoping to get the PDK reprogrammed without literally having to do a PDK relearn at the dealer. I definitely think it's helped in my case. I've never had it do it since, but it was disconcerting nonetheless.
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Spyerx

Dont lug the car. These things like to be kept on boil.