Hi, I've just bought an Audi A4 2.0TFSI S-Line and thought I'd register on here for some advice.

I bought the car privately a couple of weeks ago and didn't pick up on the test drive a 'rasping' noise that appears to be coming from under the front of the car when I lift off the accelerator, or rev it when stationary.

The best way to describe it is think of when you're free-wheeling down a hill on a push bike and you pedal backwards - it makes a sort of whirring/rasping noise. If the car is moving and in gear and I let off the accelerator it makes the noise constantly until the engine speeds drops really low, the same when stationary and I rev it.

My guess is it's related to the negative pressure in the exhaust system, so perhaps is to do with the CAT or the turbo - any ideas?

Thanks and hello!

Rich.

 

how would a vacuum pressure in the exhaust system even happen and why would it make such a noise as you describe? it didn't happen before but does now? is this possibly an example of buyer's remorse? i'm sure the system diagnostics would indicate a problem if there was one.

 

Thanks for the useful reply :-s

I've owned a couple of Subaru Impreza's over the past 5 years so know a reasonable amount about the 'mechanics' of turbo chargers, including having a PSi3 Data Monitor fitted that used to display negative boost pressure values when initally releasing the accelerator - hence my question about whether it's related to negative pressure in the turbo/exhaust system.....

It isn't buyers remorse, I'm very happy with the car just concerned about whether I may have bought a car without noticing a potential fault during test driving it. It's booked into my local main dealers on Wednesday for its 50k service so they should tell me more, just thought I'd ask for some friendly (and free!) advice first.....

Does anyone know whether there are any known or common issues with noisy CATS or perhaps issues with the shaft in the turbo unit?

 

ur problem seems to be what alot of people hear when they first get to know thier car, our FSI engines make almost a diesel sound when they are at idle or just coming down from being revved and its largely due to the direct injection motor and how its designed.....

 

rich, you're full of ****.

 

your hearing the diverter valve, very similar to a blow off valve, i upgraded my air intake and now i can hear the turbo alot more the diverter valve makes that very same sound when lifting off the accelerator. Its a beautiful sound and i want to make mine louder