2008 Audi A8 4.2 Quattro
100,xxx miles
Hello , I just bought this car and love it . It drives great except for ive noticed
a noise at a specific speed 85 to 90 mph . doesnt matter if i am accelerating
or decelerating .even when i shift into neutral the noise stays the same as long as the speed is maintained 85 to 90 . It doesnt matter if i turn to left or right the noise is still constant as long as the speed is maintained .
if i go above 90 it goes away .
any info would be greatly appreciated as i am completely new to owning this car.
i ran a scan and no codes appear
tires are toyo 255/40/r19 half tread left

 

It's probably the plastic air deflector cover under the nose fascia back under the engine. Somebody probably left some of the attachment hardware off of it. At 90mph, it's going to move around..

 

thank you Dave for your help , can you tell me where air deflector is located. Is it something i might be able to fix myself or should i take it to dealer .
thanks again for your help , i really appreciate it .

 

You can't miss it. It's the big flat plastic panel under the engine. It is connected to the front fascia underneath and runs back between the wheels. If you've ever had to do an oil change on these cars, you have to remove it to get at the oil filter and oil pan. Sometime people do not get all the attachment hard ware secured and it gets lost on the road. It's also referred to as a splash shield.. Here is one for the TT. Yours will look similar.


Engine Splash Shield New Coupe Audi TT Quattro 2008 2013 AU1228116 8J8825237A | eBay

 

Got it , front right corner fastner pulled loose . I zip tied it for temp fix . Will see if that fixes the noise . Thanks again for all your time ,

 

No problem. Let us know how it works out. The previous owner of my A8 was telling me that when he first got it, he was zipping down the road at about 90-100mph and kept hearing something hit the bottom of the car much like what you're experiencing. After a couple of minutes, it let go and start flapping.. He pulled over to see it hanging down enough to catch air. He drove home at normal highway speed with no issue but had it fixed at the shop he used. Never had an issue again with it.

 

no dice , just got back noise is still there , however it seems like a piece of plastic vibrating at the speed could be the cause

 

Check for other loose splash shield items. The wheel wells are lined with plastic shields also. Just poke around underneath and see if you find anything loose. 90mph winds can make things move around...

 

will do , and i will keep you posted .
thank you

 

well , ive installed new wheels and tires and now the noise isnt as pronounced and is more like a high pitched harmonic noise from 60 to 70 mph . the sounds is a lot softer and less pronounced but still there. it is over a longer mph range now
i can very faintly feel in steering wheel .
20" Michelin tires 255/35/20