Has anyone had bad cats or know what they sound like? I recently installed a full catback (custom) and I now here a rattling noise. Not sure how to upload a video here but when I figure it out I'll upload it. I have a '12 sedan with a custom 2.25" exhaust. When I installed it I had no issues but once I tightened up the v band clamps I'm now getting a rattle. Not sure if it's a heat shield near my x pipe or if it's the cat heat shields but it's getting pretty annoying.

 

when i had my stillen exhaust on my old g35 i had the same issue. it turned out to be a loose connection, but i would figure the heatshield first. jack up your car and take a rubber mallet and tap on your exhaust and see if you can find where the rattle is comming from. also check your clearances and make sure the exhaust is not tapping or rubbing on something.

 

Thanks for the suggestion. I'll take a mallet to it when I have some time this weekend. I looked on youtube and found a few other videos with the almost exact same sound saying the cats were no good. Maybe it's time for some HFC's or resonated test pipes. Hmmmmmm.

 

I have a similar rattle going on, its been too cold in Wisconsin to get under and check it out lol

 

Did you figure out what was causing it? I've been getting the same problem since I put on my HKS Axle Back. Been thinking it's a good time to go test pipes or HFCs.

 

I would think that if the cats were bad you would have more symptoms (CEL, poor acceleration, bad gas mileage, etc.). Let us know what you figure out.