991 GT3 - Diagnosis Help

[markrichards]

Bit of advice sought from those in the know.

The 991 GT3 has been at an OPC for 4 weeks for what felt like a gearbox issue. Grabby gear changes in auto mode when changing-up below 2k RPM. Hard to describe except that it feels like judder felt through the car. Most noticeable when hot. No issue when changing under load above 2k RPM.

We initially thought that the cause was PDK / clutch related but after two full resets and a plug-in with the ECU, we can't find the cause.

OPC then thought it could be a slight misfire and vacuum tested the whole induction. Nothing found.

We're now putting the original silencer back on (has the Sharkwerks bypass) to ensure it's not a back-pressure issue. In my view, it can't be, but the OPC won't do more work until it's ruled-out.

A beer (or five) to anyone who can shed any light etc as Porsche UK / OPC are out of ideas? Is it unreasonable to ask that someone from Germany come out to take a look if no-one in the UK can diagnose?

Cheers,

Mark

Without the car for 4 weeks is getting a little frustrating...

[PorscheGT4]

"changing-up below 2k RPM" in a GT car interesting concept.

no car is happy doing that, and I would say not great to load the engine that way either putting extra strain on your pistons, valves, etc.

I would say just drive it and change gear at 9k revs ;-)

Edited by PorscheGT4 on Friday 13th February 18:45

[markrichards]

Ha. Fair observation. Unfortunately PDK auto does just that...loves to shuffle up the gears. To be fair, convenient about town. Concern is that it's only recently become an issue, so something is wrong. If it had always happened then I'd live with it.

[robgt3]

I can only speak from experience but why is your car changing up at 2000 rpms. How slow are you driving? Mine varies its up shifts on how much pressure is applied to the throttle plus it is re -thinking that process constantly. Out for a play the other day and it was upshifting at 7000 rpm. Back into 30mph limit then it returns to normality or indeed sanity.

[markrichards]

This is normal town driving. Pulling away from lights etc at sub 30mph speeds. That's when the issue occurs. Juddering up through the gears.

On proper driving, no issue and indeed when accelerating hard it changes up much higher.

[APOLO1]

has it ever been right, or like this from the off,? ask the OPC once back to stock to re-boot the SW that came with the engine fix....if that fails, get in nice and warm and do a few LC starts....then get back to me...

btw there is a bit of drive line chatter at low speeds.....