Drivetrain Vibration (ala, "they all do that")

[Scott in Cincy]

Hi Renntech'ers

Long time member, relative few posts, just gotta use the search tool and voila! Here's something I haven't seen discussed:

My new to me 2008 Cayenne Turbo has what I consider to be very weird behavior from the drivetrain. When under light throttle input and accelerating up a hill, the driveline shudders, almost like the motor is lugging. If you give it more gas, and the vehicle downshifts, it goes away.

I took it to my trusty dealer (I do actually trust these guys), and they told me they all do that...even the new Panamera's do it. It's really a 1000-2000 rpm phenomenon while cruising, but seems like it could be fixed with different software or perhaps different motor-mounts? I thought maybe by keeping it in Sport mode (which is vastly more fun) that it would keep it from doing it, but alas, it does not.

I posted this on Rennlist, and heard from another 'lister that he had the same issue and it's not fixable. Any thoughts from the smart guys here?

[wvicary]

Sorry I have not heard of this problem before. Any chance you can drive another from your dealer to see if that one does it also?

[mchung]

That sort of behaviour is what happens to me with my 06 CS. Just when you want to accelerate smoothly, it judders a little bit like it's lugging. Not horrible bucking and jerking, but just some unsmoothness. Downshift and it's fine (of course). Most passengers don't notice it, but I do (and so do some car buff passengers). Idle is generally OK, but not as smooth as I would expect.

As I mentioned in my other post, the Durametric tool shows some misfiring. I'm pretty convinced it's a bad coil (or more).

I told the dealer that the best way to see this happen is to get the tranny into M6 (just around 55km/h I think) and try to accelerate. The dealership said that Porsche does not recommend running it that way and this is normal. I have about a month left of warranty so I would like to get it taken care of soon. I'm collecting evidence so I don't have to waste my time at the dealership again -- I'll present the TSBs, Durametric logs, etc.

Now, if my knowledge isn't off, that low RPM area should be where the vehicle operates closed-loop lambda, so some cycling of the engine may occur under steady cruise conditions as it adjusts the fueling. That may be what the dealership is trying to tell you. But it shouldn't be creating such a noticeable drivability problem especially when accelerating.

Martin

[Scott in Cincy]

That sort of behaviour is what happens to me with my 06 CS. Just when you want to accelerate smoothly, it judders a little bit like it's lugging. Not horrible bucking and jerking, but just some unsmoothness. Downshift and it's fine (of course). Most passengers don't notice it, but I do (and so do some car buff passengers). Idle is generally OK, but not as smooth as I would expect.

As I mentioned in my other post, the Durametric tool shows some misfiring. I'm pretty convinced it's a bad coil (or more).

Martin

Martin,

I'm starting to think it has nothing to do with the drivetrain myself...it's an engine speed thing. It happens between 1400 and 1800 rpm in top gear. Keep me posted on what you find, and I'll let you know what happens in the discussion with the regional tech rep that I plan to have soon.

Thanks,

Scott

[Fatcayenne]

That sort of behaviour is what happens to me with my 06 CS. Just when you want to accelerate smoothly, it judders a little bit like it's lugging. Not horrible bucking and jerking, but just some unsmoothness. Downshift and it's fine (of course). Most passengers don't notice it, but I do (and so do some car buff passengers). Idle is generally OK, but not as smooth as I would expect.

As I mentioned in my other post, the Durametric tool shows some misfiring. I'm pretty convinced it's a bad coil (or more).

Martin

Martin,

I'm starting to think it has nothing to do with the drivetrain myself...it's an engine speed thing. It happens between 1400 and 1800 rpm in top gear. Keep me posted on what you find, and I'll let you know what happens in the discussion with the regional tech rep that I plan to have soon.

Thanks,

Scott

[Fatcayenne]

My Cayenne Turbo 03 shudders a bit, but only to be expected!

[odix]

It may be the power shifting around from front to rear axels. An idea: deactivate PSM and determine if the problem remains exactly the same as when PSM is on. I notice (on my '04 Cayenne S) some subtle power transfers accelerating and decelerating under lower RPMs -- it seems odd but it is normal from what I can determine. The S does this with both PSM off and on. A friend has an '04 Cayenne Turbo which I've driven and it exhibits the exact feeling as my S.

Also, I have a new driveshaft and eight new coil packs (replaced due to failures) and plugs -- and the issue is still there. Hence my reasoning that it's normal.

Edited February 22, 2010 by odix

[Fatcayenne]

It's a bit like a large Ferry boat under power. One would expect a few noises from such a heavy beast with 450 bhp under power!

I rather like it.

[horstle]

I heard the same answer from my dealer when I showed the problem, juddering at 1400rpm up to high speed. Answer 8 of 10 are doing that. However, I asked some other mechanics and all replied that juddering/shaking etc is NOT common or usual and always a sign of out-of-centre parts.

key problem is juddering periodically and stronger in high speed range between 230-270km/h.

Did you try when the gear-selector lever on Park mode if the car is still juddering between 1400 - 2300rpm? if yes, it´s something withe engine, torque converter or gearbox.

[Fatcayenne]

I tried mine today, just to double check, and there is no vibration at all.

There is a noise like an electric train pulling away, when accelerating hard, but it's perfectly smooth...

[boyer2003]

My 2004 S behaves similarly to your description occasionally. It almost reminds me of driving a car with a manual transmission and coasting at low rpm in one of the higher gears. I get a slight shudder and once I accelerate, its fine. I chalked it up to the German engineering interpretation of the automatic transmission? Good Luck.

Hi Renntech'ers

Long time member, relative few posts, just gotta use the search tool and voila! Here's something I haven't seen discussed:

My new to me 2008 Cayenne Turbo has what I consider to be very weird behavior from the drivetrain. When under light throttle input and accelerating up a hill, the driveline shudders, almost like the motor is lugging. If you give it more gas, and the vehicle downshifts, it goes away.

I took it to my trusty dealer (I do actually trust these guys), and they told me they all do that...even the new Panamera's do it. It's really a 1000-2000 rpm phenomenon while cruising, but seems like it could be fixed with different software or perhaps different motor-mounts? I thought maybe by keeping it in Sport mode (which is vastly more fun) that it would keep it from doing it, but alas, it does not.

I posted this on Rennlist, and heard from another 'lister that he had the same issue and it's not fixable. Any thoughts from the smart guys here?