I had been trying to troubleshoot this noise that was driving me absolutely insane for the last several months. It's somewhere between a flutter and a rattle – at times sounding like some kind of airflow leak and other times more metallic. I thought it was coming from around the driver's side front cat.
Fast-forward to about 3 weeks ago, I brought the car in for some maintenance/service – new battery, valve cover gaskets, rear tires, some other small stuff. The shop diagnosed the noise as coming from the gasket between the headers and primary cats (which after researching, seems like a somewhat common failure point on these cars). The car sounded/felt fantastic when I picked it up and for about a week after, at which point the noise started gradually returning.
It's now louder than it's ever been, and I feel it's affecting the performance of the car. Throttle response seems a little sluggish – especially at lower RPMs, idle isn't quite as smooth, "hiccups" a bit on cold start.
The obvious hypothesis is that it was in fact the gaskets, and for some reason the new ones sprung a leak. But, I wanted to post here to see if anyone's had a similar experience and can confirm I'm on the right track.
A few observations:
- Noise starts with about 30% throttle in any gear
- Any RPM, but most pronounced between 2k and 4k
- Becomes loudest at about 50% throttle, then tapers off a bit at WOT
- Seems to get louder and come on with less throttle the warmer the car gets - it will be more pronounced at the end of a drive than it was at the beginning
Finally, I drove up on ramps today to investigate and took a few videos. Driver side seemed notably noisier when cold.
Driver Side - Cold Start:
Passenger Side - Cold-to-Warm:
Driver Side - Warm: