britinmn

A question for any other W12 owner out there - mine is a D4, but would appreciate any D3 input as I think my D4 W12 is pretty lonely on the D4 forum I have posted this over in the D4 forum just in case anyone has any ideas...

Either a) this issue has just recently got worse/popped up, or b) I have become more sensitive after having got used to the smoothness of the W12.

Car is a 2013 W12 with 96K

The issue is a 'weird' vibration. I have had other people feel it so I am not going crazy here lol. Engine starts cold/hot just fine, no codes etc. At idle it appears to have a little 'roughness' is the best way I can describe it. Nothing crazy, but definitely not super smooth. With the car in park and stationary if you feather the gas you can feel a vibration in the seat of your pants that also runs through the body of the car. Feels almost like a slight miss. It appears worst at 1400/1800 rpm where you can just hold the rpms by very lightly feathering the throttle. If you touch the body of the car you can feel it through the car. I can duplicate this while driving in the same rpm band with the same feathering of the throttle ... usually at 60 mph or so in traffic... the vibration is very noticeable (at least to me) and gets worse when driving in that rpm band if you give it gas to accelerate, when it turns in to more of a 'shake'.....

Before I noticed I could duplicate this in park, I first thought the vibration could be suspension/tires. Swapped out the front upper and lower control arms and sway bar end links - all were worn but not completely shot. Of course the vibration did not change. Changed out spark plugs but the old ones did not look fouled, checked throttle bodies and intake runner while we were in there, air filters, MAF sensors etc. and guess what.. no change of course.

I have hooked up our shop scanner numerous times - no codes, nothing 'weird' that jumps out at me while looking at live data with the engine running. Unfortunately our scanner can only graph data from one module at a time so we can't graph data from both ECMS at the same time to see if there is any discrepancy.

Next we will put it on a lift and disassemble the myriad of under engine shields to see if there are any vibrations apparent - thinking possibly a flex pipe issue that the Turbo'd V8 seems to have on a fairly consistent basis. Maybe a bad engine mount?? or ???

Any ideas/feedback would be greatly appreciated!! I absolutely love this car. Any other car I would probably just brush this off and try to live with it until we could figure it out, but this is seriously bugging me as this car is supposed to be so smooth.

jugge2

Bad mount

MP4.2+6.0

Search on the D3 W12 torque mount. I posted on it in past on D3 board, and a couple other D3’ers lost it too. It is the far forward mount on US passenger side. Somewhat more noticeable or hard feeling shifting at full throttle could be another symptom.

TSHong

+3 on a bad mount. The W12 is just silky smooth and since no codes, probably not an engine misfire issue.

MainelyA8

I have similar symptoms, but on a D3 4.2. Very slight vibration when stopped now, and also a slight stutter when taking off from a start. Is there way to confirm it's the mount with VCDS?

MP4.2+6.0

Main mounts will code for an electrical issue. None of them code for a physically broken type issue. You have to inspect for the latter, looking for big cracks and/or the brownish leaking hydraulic oil that is inside them.

pocketchange

If you cannot locate an issue, try a bottle of Marvel Mystery Oil. Put it in both Gas & Oil.

I've used it for years due to only being able to only putt around and not driving the way it was designer to be driven..
MMO will keep upper cylinders and valves from gumming up and the engine clean for about as cheap as anything. pc

(I own Marvel Mystery Oil (i wish.)