ThePiombino

Good morning B8 gurus!

Have a question for you all. Lately, I've been experiencing what I feel is a slight loss of power. To go along with this sudden (butt-dyno-verified) loss of power is the occasional cylinder misfire (verified via VCDS diagnostic).

Last night, for the very first time, I heard what can only be described as a fluttering sound as the turbo spools down. As I lean on the gas the turbo spools up as intended, seems to sound fine and once I lay off the throttle it makes this weird fluttering sound (almost like a weird bird or something like that).

Weird thing is that it DOES NOT make this noise when I hit the gas at idle. Only when the car is in motion.

Does anyone have ANY ideas here?

*EDIT: Or would it make more sense that it is the DV failing?

takethetest

Is this the sound it makes? This is perfectly normal for a turbo. I know the B8 makes this sound when lifting off of medium to full throttle, it is definitely not as loud as this guy though.

http://www.youtube.com/watch?v=baUEBAKw5vQ

QUA77R0

ThePiombino,

The DV does make a noise similar to what you describe. How many miles are on your car? Did you never notice this "flutter/whistle/chuff" before? Is it getting louder?

I was about to dismiss this as you are merely describing the normal sound of a DV. Some FI cars suppress the noise more than others whereas some people add loud DV's just to get the sound...

What you describe has nothing to do with turbo failure so I wouldn't worry about that. Since you ARE experiencing some power loss and a misfire, it seems that something is not right.

I did have my intake replaced under warranty recently as the DV failed and the valve is molded into the intake. I had reported on a repair order about 6 months ago that the DV noise seemed to have changed somewhat (they couldn't find any problem). Then one day it just went bad. The symptoms for me were a mild surging one afternoon that got really bad on my way home. Foot fully on the brake and the car was surging at a red light attempting to pull forward and the Christmas lights in the gauge cluster were imitating a disco. I have experienced similar symptoms in Volvo Turbos that had air leaks from split hoses. I checked hoses but found no apparent split. Once home, the car would not restart. Audi paid to flatbed the avant the 60 miles to the nearest Stasis authorized dealer. Intake/DV replaced and no problems since.

I can't believe that Audi molded the DV into the intake. I can't wait till they fail once the car is out of warranty... Having to replace the intake to replace a faulty $30 valve is absurd. At least it was on Audi this time.

ThePiombino

Unfortunately I'm no longer under warranty so I'm hoping for the best here. As far as I can tell the car never made this noise prior to this past week. I brought it to my mechanic who seems to think the car is pinging and that it's due to a bad batch of gas I recently filled up with. He suggested I throw in a bottle of octane booster (which I did) and run the tank close to empty and fill back up someplace that I know has good gas. I'm not sure why a bad grade of gas would cause the DV and/or turbo to make a weird noise, nor do I hear any pinging, but I know that he isn't trying to "take me for a ride" since I was charged nothing for the diagnosis. Now did he suggest he do any work to the car. It's been 2 days since the octane booster and it's still making the noise. Granted, there's still a 1/2 tank of the "bad gas" to go.

QUA77R0

"bad gas"? As in water or contaminants? As in wrong grade/octane?

I have heard plenty of pinging over the years on other cars that I have owned and for the life of me, I can't see that sounding like the "fluttering" which you initially described. I'm still betting on a DV that has begun to fail. I'm not sure whether we have a plunger or diaphragm type DV but either way, once it fails, you won't be driving anywhere. For me there was a 3-4 month window from when I first reported an increase in volume of the DV noise. At that time, I was told it was within spec/normal... Obviously it WAS failing as it died catastrophically a few months later.

I understand that you also have that misfire which may or may not be related. Anyways, now I'm very curious as to the resolution.

ThePiombino

Despite being skeptical of the initial diagnosis (bad gas), I followed the mechanic's advice and ran out the tank with a bottle of octane booster and refueled. Still experiencing the same sound. This is perplexing as it only happens when the car is in motion. It does not happen when in park or neutral, even during heavy load...