I thought it was one of my Catylitic Converters but the dealer says no. They are pretty sure its a fuel/ignition type problem but don't know how to solve it without charging me a ton of money to do random things that may not work. Its a 2002 S6 Avant with 50,000 miles, when the car is warm (a bit before operating temp and up) an annoying and loud rattling noise occurs when I'm hard on the gas. I love the sound of this car but this rattling noise just ruins it. Driving me crazy. The dealer changed the plugs thinking that would solve it but it did nothing. They're next idea is to do a full fuel/ignition system cleaning for $500+. Any ideas? Thanks for any help!
Tim

 

I've been getting this just recently. It mostly (but not always)happens when I stomp it (ussually in 2nd) after just cruising along- easy accel -in the prior gear - its also happend in 3rd a few times. I hear metalic rattling sounds - sometimes very racous (on occasion frighteningly loud & bad sounding)- but ussually more like engine pinging/valve sound. First I thought it was commming from my exhaust (AWE) - and in fact some clamps were loose a bit. And it may still be this. But my mechanics think it is pinging caused by bad gas (not sureI fully buy it - but who knows). I'm worried that I may have some valve wear or something similar. Bottom line I don't know. Heard it just slightly today. Doesn't seem to impact performance - as far as i can tell. Anyway - my mechanics recommended Shell & BP gas - which they say has a less harsh detergent profile. They also warned about ethenolized gas - but hard to avoid sometimes. I'll let you know if I find out anything definite. I'm worried that I'm going to blow a rod or something similar - but my mechanics seem to think its something minor...still might be the exhaust even...

 

BTW I did just change out the plugs for exactly this reason - no change.

 

probably not likly but what about a rusted out exhaust hanger??? Im sure the dealer looked but just a thought.

 

Yeah my dealer told me it could be bad gas as well. I didn't buy that though. Its been making this noise consistently for about a year. I've also had the car at an exhaust specialist and they made sure everything was tight and that the cats and exhausts were ok. I notice itstomping on it in 2nd gear mostly too. I also notice it inall other gears basically though. Not so much 4th and 5th because then Igoing too fast.I'll keep you posted if I figure anything out as well. Glad to hear I'm not the only one with this problem. And yeah it doesn't seem to effect performance in any way, just an annoying sound from a car that does and should sound fantastic. Kills me to hear it. I might go through with the fuel/ignition system cleaning that the dealer has in mind. I'll let you know. Thanks guys
Tim

 

could you post a sound clip? Does it sound metal on metal?

 

Mine does sound like metal on metal (particularly when it is bad) - it might just be the exhaust pipes (I have AWE) rattling against each other IMO...hard to say - annoying when I hear it.