wheeler

Thought I would bump this topic again. I think this solely relates to MANUAL cars, not sure you would even feel it in a PDK.

But driving a lot again this Spring, the hesitation/stumble at 2700-2900 is still there. It's most pronounced and most annoying shifting from 1st to 2nd. Occasionally I will feel it when rolling in 2nd gear slow and accelerating through that rpm zone.

Seems to me like a vari o cam type thing. And it's only noticeable really in the "normal" shifting situation, just leaving a stop light, running up to 4k or so, shift, drops down to 2500 rpm and will feel the hesitation right when you get back on the gas in 2nd. Makes it difficult to get a smooth shift without the car jerking a little. If you short shift it OR run it up to say 5500 rpm and shift you can't feel it.

I may try the dealer again and see if I can get a tech to ride with me or drive with me. I've got a CPO for another year or so, but I get the feeling my dealer here is not interested in figuring it out. Just thought I would see if anyone or anything new had popped up??

jeffrec

Wheeler...I also have a 2009 C2S with manual transmission (27K on the clock) and have the same problem. I just posted a similar topic on the PCA technical forum to see what their experts have to say. What I have noticed is that it seems to be worse after the car sits for several days. I plan on getting her out of the garage this week and opening her up on the highway on my way to work a few days. I'll let you know if that makes any noticeable difference. My car is under CPO until August 2015 so please let me know what the dealer tells you.

wheeler

Got a fault light for the TPMS, so I'm taking my car to the dealer soon. Were you ever able to get anymore info on your end? One thing I'm wondering, are you running all stock exhaust? I have the fabspeed x pipe and have read some things where X pipe can cause a rough idle in SOME cars. I bought mine with the X pipe so no idea what it was like stock.

The hesitation/miss is still there, probably more often than not. Doesn't seem to matter if the car is cold, warm or hot off a drive. I have noticed, again, that driving in sport mode the throttle feels "cleaner", like the fuel mix is more right...if that makes sense. Doesn't seem to be as "fat" feeling off the bottom (to use a jetting term). Only problem is in sport mode the throttle is so touchy it's hard to drive it smoothly in traffic. But the shift from 1 to 2 is perfect and smooth in sport mode. It's a train wreck in normal mode...unless you really try to feather it. Now if you're ON it hard, you're well above the target RPM range of the problem. Man I wish they could figure this out.

wheeler

Okay...not sure how the hell I missed your post back when this thread was going!?? THIS procedure actually works! I've been trying the last 4 days or so and the 2800 rpm stumble has virtually disappeared. I say virtually, as I WATCH the tach go past 2800 I can still feel a little something, some kind of transition happening, but NOTHING like before. This issue has been progressively pissing me off more and more lately, just total bull$hit Porsche won't address it.

Bruce In Philly

Mine has dissipated quite a bit after I installed the Sharkwerks X pipe. I don't know why except maybe there is less back pressure. There is a flap in the plenum that flips at about the same time as the valve lift transitions.... maybe the change in back pressure affected the flap flip.

I dunno.......

Peace
Bruce in Philly

wheeler

Ya, I've got the Fabspeed X pipe...had since I've had the car.

This throttle blip thing really works!

Petza914

I don't think taking your just started totally cold engine up to 3,000-4,000 RPM is a good idea even if it does correct or minimize the stumble issue. That has to be a prescription for scored cylinders, thrown rods, or worse, especially if you live where it's cold and drive your car year-round. There has been a little talk of the DFI engines already washing the cylinder walls by squirting fuel directly into the combustion chamber, and revving the engine where it squirts more fuel in before the oil is circulating well would only exacerbate that issue if it exists. It's your car so do what you like, but if you've been able to circumvent the issue with this procedure then Porsche should certainly be able to figure out the right way to correct it instead of this potentially damaging method. What happens if you warm the car up by driving at lower RPMs, then after it's warm you do a shut down and restart? If the issue is truly tied to the warm-up idle prototcol the car does and you restart the car where it doesn't need to go through that process, does it then drive normally? If so, and it were my car, that's what I'd do, just shut it off and restart it at a traffic light until Porsche can figure out the right fix to the problem. Is that a pain and annoying, probably so, but so is having to replace a $25-$30k motor

wheeler

Relax, It's just a quick blip, at least when I do it. Doesn't even go past 2500 to reset it. And it does work. I do agree blasting it to 4k not a good idea.

EMC2

Interesting thread. I had my PDK module software updated for a shudder that would occur if pulling away with little or no throttle. It fixed the issue, but it also made the PDK shifting significantly less aggressive (particularly in sport plus mode). I'm sure it's better for the gearbox, but it is nowhere near as fun as it used to be.