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D4 W12 engine vibration ?

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Old 10-12-2017, 05:58 PM
  #1
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Unhappy D4 W12 engine vibration ?

A question for any other W12 owner out there - preferably D4, but would appreciate any D3 input as I think my D4 W12 is pretty lonely on the forum I will post something over in the D3 forum to see if any of the D3s have ever come across this.
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.

As a side note - called Audi to see if there were possibly any powertrain software updates - none that they could find, but they did find an open recall on the coolant check valve.... took it in the next day, and they confirmed seepage into the harness. Valve replaced and wiring harness section replaced, but did not change anything with the vibration symptoms. The tech supposedly took it for a test drive to see if he could diagnose the vibration but came back and said he could not replicate.
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Old 10-13-2017, 06:06 AM
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Sounds like the flex pipe issue on my 4.2. Try having an exhaust shop replace them. Got mine done for $300, problem solved.
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Old 10-13-2017, 02:08 PM
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Go to a dealer!! Engine mount.......torque converter......who knows. You are ONLY guessing unless it is scanned. I for one wouldn't even drive it till its sorted out, you DO NOT want to risk driveline damage!
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Old 10-13-2017, 08:38 PM
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Thanks for the input guys - from the post on the D3 forum, the consensus on the D3 W12 with these symptoms is an engine torque mount on the right front of the motor. After digging some more today, I don't think the D4 W12 has the same mount, and instead has twin torque mounts (that maybe are even solid mounts ?) one on each side of the front of motor.

However, after finally getting a chance to get it on a lift in the shop and get the under engine shields removed, low and behold we find dark fluid dripping out of the subframe where the right engine mount mounts, and dark fluid on the bottom of the engine mount itself. So right now our guess is that the right engine mount is done As I value my employees (lol) I think I will have the dealer replace at a cost of $1,650..... Which I think is pretty darn reasonable as looking at the replacement procedure it looks like a huge pita !! I think the Audi book time is 8.7 hours - I pity the poor tech that works on it as I think he is going to earn those hours!

As for taking it to the dealer - it had been to the dealer on Tues/Wed for the engine coolant valve recall at which time I asked them to investigate the vibration - the report back was that the Tech could not duplicate the vibration, and had 'fixed' a bent exhaust hanger which may have been causing a binding in the exhaust, but as there were no codes, they were not sure what the vibration, which they couldn't duplicate, was. Which is exactly why I like to know, if not for 100% certain, as darn certain as i can be what any issue is before anyone that doesn't work for me touches any of my vehicles.

I will post pictures of the engine mount tomorrow ......
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Old 10-13-2017, 10:49 PM
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Originally Posted by britinmn View Post
Thanks for the input guys - from the post on the D3 forum, the consensus on the D3 W12 with these symptoms is an engine torque mount on the right front of the motor. After digging some more today, I don't think the D4 W12 has the same mount, and instead has twin torque mounts (that maybe are even solid mounts ?) one on each side of the front of motor.

However, after finally getting a chance to get it on a lift in the shop and get the under engine shields removed, low and behold we find dark fluid dripping out of the subframe where the right engine mount mounts, and dark fluid on the bottom of the engine mount itself. So right now our guess is that the right engine mount is done As I value my employees (lol) I think I will have the dealer replace at a cost of $1,650..... Which I think is pretty darn reasonable as looking at the replacement procedure it looks like a huge pita !! I think the Audi book time is 8.7 hours - I pity the poor tech that works on it as I think he is going to earn those hours!

As for taking it to the dealer - it had been to the dealer on Tues/Wed for the engine coolant valve recall at which time I asked them to investigate the vibration - the report back was that the Tech could not duplicate the vibration, and had 'fixed' a bent exhaust hanger which may have been causing a binding in the exhaust, but as there were no codes, they were not sure what the vibration, which they couldn't duplicate, was. Which is exactly why I like to know, if not for 100% certain, as darn certain as i can be what any issue is before anyone that doesn't work for me touches any of my vehicles.

I will post pictures of the engine mount tomorrow ......
The torque mount is also hydraulic fluid filled, so if you find a dark brown heavy oil type fluid—or stains from it—those are strong clues about the mounts. I suppose there could be two torque mounts (besides the two engine mounts), but normally there is one. Like name sounds, its purpose is to resist the twist of the motor and drivetrain when it is under load. On D3 at least, they had no electrical modulation, so there is no code that would/could show up for them. Thus, you inspect physically. If it is a torque mount, also then be wary of the main motor mounts. They take lot of stress when torque mount has failed.
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Old 10-14-2017, 07:39 AM
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I just had my passenger side done, although I have a much smaller engine but it was bad at 67k miles. I was hoping my CPO would do both at the same time. It's interesting how the flexing characteristics change. I want my drivers side replaced. Most vibration issues go back to motor / torque or transmission mounts.
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Old 10-16-2017, 01:28 PM
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I am looking at one of these beasts, what has your experinience been with the car, specifuically maintenance, but also overall experience. How many miles where on the car when you bought it etc.
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