In regards to the O2 sensor swap, in a few cases, including mine, there has been a marked improvement. My car isn't completely cured, but I'd have to say it's undoubtedly 80% better. The stumble has turned out to be a very complex problem, as no single fix seems to have cured it completely.

Once again, hats off to PCNA for all of their hard work in resolving this.

 

Does anyone know what percentage of 991s have this issue?

 

Canadian editions only. Must be related to the cold air or maple leaves stuck in the exhaust.

 

 

After a 30k miles oil service on my 997.2 which included switching from 0W40 to 5W50 oil it seems the stumble is much less apparent if not gone for now. Will observe closely if it stays that way...

 

This really pisses me off, we Canadians are always getting screwed.

Anyhoo, thanks for letting me know. I have made an appointment with my dealer for this afternoon to have them inspect the exhaust for debris and inquire why I wasn't informed of this potential issue when purchasing the car.

I suspect this will cost me a small fortune but for peace of mind...

Thanks again, this forum is truly a godsend.

 

The Canadian part was a joke ... no need for an appointment

Only affects yellow cars.

 

LMAO.

 

I agree it's most likely not a carbon buildup issue (I had the stumble since early as well), but I've had two independent Porsche mechanics suggest it. I'm willing to investigate just to get it off the list of potential causes.

 

 

 

 

I'd never install software that is not recommended by my Porsche dealer.

 

 

I actually installed Cobb OTC mapping, the stumble is actually more noticeable. As the car pulling harder and faster, then all the sudden hit that stumbles in certain RPM, and then pulls again.