2016 C7 RS6 Performance "judder" - help please

[Tivo]

Hi guys I'm looking for some help please. My C7 RS6 (2016 Performance) has an intermittent "judder" under light acceleration from about 700 - 1200 rpm. Some days it is not there, some days a little noticeable, other days it's jerky. It's always gone after about 30 minutes of driving.

No faults found on the reader. Can anybody steer me in the right direction please? Front tyres were heavily worn, then replaced recently - am wondering if i have thrown own the Quattro somehow but it is the same with ESP on/off.

Under medium to hard acceleration it is not there - even if is a low RPMs.

Cheers.

[Adrian E]

Same tyre model refitted? Personally always put new tyres on the rear and swap to the front as they have an easier time bedding in on the back and last longer overall

I’ll have to investigate details in elsawin but if the older tyres aren’t the same age you may get enough rolling radius difference to be a problem if there’s a big tread depth difference

[Tivo]

Thanks Adrian. Good point - but not such a tread difference between the two - although there is one. Will add it to the list.

Dr G about these days still - any wisdom please sir?

[Dr G]

I don't imagine rolling radius would make any difference there; centre diff will barely notice it.

No one answer here.

Where do you feel the judder from? Steering wheel? Through the seat/floor? Brake pedal? Can you describe the sensation in any more detail?

These types of things are very subjective and can be equally difficult to pinpoint.

[Tivo]

Thank you Dr G. It occurs under light acceleration 700-1k rpms and is felt through the throttle I would say - like a learner driver judder/judder/judder. Traction/ESP on/off does not impact and weirldy some days not there at all....

[Tivo]

Could well be a repeat of this - will go after the plugs....
https://www.pistonheads.com/gassing/topic.asp?h=0&...

[Dr G]

Feasible, but be careful not to blindly throw money at the problem. That's a surefire way to make you resent the car.

Is the car's history up to date? Has it had plugs and diff oils changed to schedule?

Do the gearbox and differential modes make any difference?

[Tivo]

Thanks again Dr G. It's due a 50k service now and booked in, asked them to do plugs at same time as not been done. Will check if diffs done also. And try Dynamic Mode for the next few days.....S or D or the gearbox the fault can happen in either.

[Dr G]

Make changes one at a time if you can; use the individual mode and switch the diff between comfort and dynamic with everything else in auto. Unlikely to be the issue but pretty simple to eliminate.

Otherwise unless it's saving faults it'll be a game of watching live data on injectors, timing, boost etc. and seeing if/what is out of specification. Does it start and idle normally? Any difference in the behaviour if it's still on fast idle?

Send me your chassis if you like and I'll see if anything is due on service.

[gotoPzero]

I had a similar issue on a Range Rover.

I did coil packs, mafs, spark plugs etc but nothing sorted it and came and went.

In the end it was early signs of the torque convertor on its way out.

Obviously a very different car so might not be it but something to consider if you end up with no answers.

[Dr G]

gotoPzero said:

In the end it was early signs of the torque convertor on its way out.

I've never seen it on an RS6, and I had wondering the same. Not an easy thing to test or diagnose mind you. Had the behaviour been different across the drive and sport settings (different idle/launch RPM etc.) I'd perhaps have leant more in this direction. At this sort of engine speed the torque convertor is doubtless "slipping" and if something was wrong here could that judder? I imagine so.

It's also the sort of engine speed that the manifold flaps will be moving around to optimise low-speed airflow.

Edited by Dr G on Thursday 9th November 13:18

[Tivo]

Thanks Dr G. It has been very well behaved recently and I had almost forgotten about it. But did it a little today - last weekend the Emissions Control light came on for a few seconds.....perhaps it is related. See what the service comes up with. Such an awesome car, I hate when it's ill ha ha!

[Dr G]

Lambda sensors are common on those and often start as sporadic faults. They're expensive from Audi but pretty sure they're fairly generic parts. Sling the part number into ebay and lambdas are often Bosch parts used across numerous cars.

[popeyewhite]

Does the judder occur more when moving off from a standstill, particularly when the wheel is turned, even if slightly?

[Tivo]

Thanks - but no, straight line thing once rolling (so hopefully not diff related etc)

[popeyewhite]

Sure, but doesn't have to be the diff, could be a controller ECU. Long shot admittedly, but happened to me on a Golf.

[Tivo]

hi guys - update - the new plugs seem to have fixed the issue! Thanks for the contributions.

[gotoPzero]

Good result. 50k is about as long as I would want to leave them.