First of all, I'm talking about a 1996 Volkswagen GTI 2.0 w/ 102k miles, 5 speed transmission, and new cat-back exhaust.

I noticed last night when I left work that there is a vibrating sound coming from the car when I rev it to about 1700-2000 rpms. It sounds like a vibration coming from around the catalytic converter area. I was thinking it could be the shield around the cat that is vibrating, but I'm not sure. I've had the car since it had 90k miles on it, so I've put 12k miles on it, and I put the exhaust on at 99k miles. It hasn't made a sound until now, so I'm pretty sure its not something that I did. Does anyone have an idea as to what the problem could be? Thanks
Tom

 

Best way to find out is get under there and look.
Ive had a million noises in the other cars ive had from bad cats to squeeky springs to heat shield rubbing drive shaft on my lowered truck. it could be anything, you just gotta find it.
If its something that goes up with rpms or only does it with rpms, it most likely has something to do with the engine, i.e., something in the exhaust according to where you placed it.
If it happens at random, or when you hit bumps thats a whole other story usually. something more like a heat shield or piece of plastic would be more likely.
get under the car and have someone rev it a lttle you can tell a lot better where its coming from
good luck

 

change your car

 

I looked around and it seems to be coming from the catalytic converter area. It's hard to tell, but my friend thinks it could be the downpipe. I checked all of the exhaust hangars and they seemed fine. Maybe I'll just start driving my turbo Miata a little bit more, b/c right now, my car sounds like a 1983 CRX. I'm also going to my friends shop to take a look at it up on a lift, maybe we'll see something there. Thanks
Tom

 

could easily be the cat, eventhough its new and all.
hit it with your hand, if it makes the noise, you know...

 

Get some heat resistant gloves and tug at it while your buddy keeps it in the vibrating range, one loose connection will have that thing making all kinds of weird noises, and if its vibrating its screwing up your exhaust scavenging as well and in some cases ive seen more serious vibration cause reversion (exhaust getting back into the combustion chamber)

 

Better check your volkswagen catalytic converter, you may not experience a problem now, but you may have a problem in the future... or better yet ask your mechanic to check it... Beside a noise is not a good sign...