2005 C2 Cab

Rev the engine and at approximately 3,000 RPMs a strange raspy rattling sound comes from the rear. It reminds me of the sound of the loose heat shield on an old clunker I once owned. It occurs when sitting parked and blipping the throttle and accelerating from a stop. Strangely it goes away after revving 1-3 times only to come back again if I let it idle for a minute or so.

Dealer diagnosed a problem with the right catalytic converter a couple of weeks ago, order the part, and replaced it today. They handed over the keys tonight and I sat in their parking lot and revved the engine. Low and behold the noise was exactly the same as before. Apparently there was nothing wrong with the right Cat!!! But now they have no clue where the noise is coming from. We discussed the possibility it could be the left catalytic converter. But now they're really guessing.

Anyone have any prior experience with a similar problem?

 

It sounds from your description like a loose weld on a baffle within one of the converters. Perhaps they got the wrong one? I;ve never run across this on a Porsche automobile.

 

Maybe loose baffles inside one of the mufflers? I just had my left PSE muffler replaced under warranty for that reason.

 

I remember a similar post over a year ago, and it was a baffle inside the muffler.