2012 991 rough idle engine stumble
 

anyone experience this:

So i'm out driving yesterday and get on the highway move the PDK shifter to the left and move it forward and backwards and notice that it will not up/down shift to another gear (full auto mode working fine), exit highway and come to a complete stop and i notice that the idle is rough (more than normal) and the car sort of shudders/stumbles when i accelerate from idle.

Pull over and turn car off for a few seconds and restart and the car is still idling rough almost like it may stall in non sport mode, i press sport button and idle improves but not like normal. After restart the PDK is working fine and shifts normally in manual and auto modes.

Got home car in garage, i listened to it idle, no strange noises from engine but idle is lumpy like a high performance cam idle. No idiot lights or messages from the car, Car is stock other than the COBB ECU tune and under warranty so i will be scheduling an appointment...

you sure about that being stock thing? :) maybe start there....

Suggest that you log some pulls some pulls in the normal mode and send the logs off to Cobb for analysis. There could be a few reasons for what you experienced.

Also, be sure to remove the tune prior to going in for service.

i was wondering the same although i installed the COBB upgrade a few months ago with no issues. Its not a daily driver so i did not drive it to work, but i plan to uninstall the COBB and switch back to factory ECU map this evening and see if it makes a difference.

Can't speak to the COBB tune..

But I had similar oddness over a several month period which progressively got worse. Lopey idle (felt like it was going to stall), periodically when I started to accelerate it would it would feel like it was "popping out of gear", but it was the dual clutch somehow disengaging.. No codes thrown..

However if finally got worse and threw a host of codes and a bunch of "red" drive-on messages. Could turn off/on car and it seemingly recovered.

In the end it they ended up replacing the throttle body and that solved it. The weird PDK behavior was never diagnosed, but since it went away with the throttle body change it was obviously related (although Porsche had no explanation, but then again I was underwhelmed with their lack of insight on a lot of things).

Not saying yours is the same, but I had lopey, rough running, hesitation and odd PDK behavior. At first it wasn't a big deal but gradually got worse.

that describes what i was experiencing, i didn't get a chance to drive it the other day, but i did start it in the garage, and the idle seemed normal but I only let it run for about 1 minute, will take it out tomorrow after work and see if it corrected itself...

1. You'll have to remove the tune because Porsche will blame everything (including a flat tire) on the tune.
2. If you go to the dealer with the tune they'll claim that you voided the warranty by installing the tune and charge you a fortune.

I realize it's a royal pain, but start with #1 if you plan to go to the dealer..

I agree 100%, so had a chance to re-vist the car today and drove to work about 16 miles but its to downtown DC so not a fun commute. it started up fine and idle seemed normal for about the first 8 miles, then I noticed the lumpy idle, hesitation, and reduced power. So on my drive back home it started to get worse and then I got a message "fault engine control, possible to drive on", so I continued to drive and then 2 more messages "deactivated the stop start function and then PSM was deactivated" car was running really rough and thought maybe I should pull over and have it towed, but each message said ok to drive on.

So uninstall the COBB tuning, but first I look at the codes and there was about 5 codes that mentioned Misfires and 3 or 4 under PDK, I was able to restore OEM map. Started car and noticed the message were gone, but I did take pictures of the messages with my phone, was able to schedule an appointment on Monday at the dealer, so I will just let it sit until then. will post back the results of the dealer visit next week....

Multiple misfires, hmm sounds familiar. I would guess that there is a valve train issue. Please keep us posted.

1) try things from baseline (now that you are at it sans tune)
2) have you checked on RL? will get a LOT more info/fback

Just got a call from the Dealer they are replacing the Valve Lift Solenoid, had to order part car will be ready tomorrow covered by warranty....

That's great news. Glad they were able to diagnose quickly. It sure sounded like a valve train issue.