Puzz1

I know the vibration issue has been discussed a lot for the 4.0. Not sure if I have the same down pipe issue but I'm starting to get a vibration when I start to slow down for an intersection, stoplight, etc. I hear it more often. Started out to be intermittent about a week or so ago. Now it's every time I drive the car. I recently put new tires on. I hope it's not related. Any thoughts prior to bringing it in to dealer ?

mtnboydl

A few basic things to help you on the diagnostic path:

Is it while you are braking (and only while braking)? If so, you could be dealing with warped rotors or something on that line.

If it is a vibration while idling, but goes away when you increase the RPMs to 1-1.5k, likely a vacuum leak somewhere in the engine.

Finally, try putting the car in neutral at speed. The engine will immediately go down to an idle and possibly eliminate engine sources of vibration while you slow the car.

MP4.2+6.0

+ 1. In addition, OP says "I hear it more often." I assume you really do mean hear it, as opposed to feel it. Describe any noises. Clicks? Creaky? Rumblings? Grinding? Squeals? Other? Any changes while turning in either direction, and either at speed or more slowly?

Puzz1

Its something that I feel and hear at the same time. Hard to describe. Seems to be emanating from under the car somewhere. I hear/feel it when slowing down before braking - like when I lift off the accelerator when approaching a light or stop sign. Happens at low-rpm - under 2000rpm. I read of a similar issue on the A7 board and it was related to a bad motor mount. I would describe sound/feeling it as if I drove over a very light rumble strip on the highway - meaning that if a normal rumble strip is a 10 on a scale of 1-10, this would rank as a 1 or a 2.

mtnboydl

So you feel it when you're not braking, but rather coasting?

What about at an idle? Any roughness or noise?

Motor mounts will vibrate im relation to engine RPMs (+/- under a load which it sounds like yours isn't)

Take a few minutes next time you drive to isolate a few things while going down the road, as mentioned above.

You mentioned the downpipe issue in the 4.0, but that is a turbocharged engine with a very different downpipe system.
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EleganceA8

EleganceA8

porboy44

Try reving the engine in neutral. My 3.0t had its vibration fixed with new downpipes. It would vibrate at the same rpm while driving and in neutral. I also took a video with my phone of the flexpipe and you could clearly see it vibrate at the rpm where the issue was. The flex pipe was also visually "worn" and could be heard leaking on the video.

Puzz1

I did the rev test and sure enough it vibrates at around 1200 to 1400 rpm. Thanks for the tip. Will bring it in soon.

snowsnob

Can anyone give an idea on cost of replacing downpipes at Audi? Or did you take it to indy? My 40k service appointment is in few weeks. I had this issue for awhile now but due to being so busy with life I was waiting to bring this up during oil change. Car is out of warranty now.
And what exactly do you mean by downpipe. Thx