Rep Power: 0

I have a 2001 Civic EX Coupe, and about 4 months ago I installed a RS-Type N1 exhaust, I kept the cat, and replaced all the piping behind it with 2.5". A couple of days ago it started making this rattling sound when I either was at 1000-2000 rpms. It only really does it if I'm either downshifting, or if I'm just cruising at that rpm range. I already removed the heat shield from my cat, so it can't be that, but I don't know what else it can be. I'm thinking some kind of weld has broken loose, or stuff from the cat is coming out, and is getting stuck in the muffler. Has anyone ever experienced this on a car like this with a n1 style exhaust?

 
Rep Power: 512

Where is the rattle at? Rear by the muffler? Under the shifter console? Engine bay?

When I first put the Apex'i WS2 exhaust on my car, had some noise coming from the muffler area. Ended up being the muffler rattling against the underdog. Found some (stiffer) urethane exhaust hangers to decrease muffler movement and, for good measure, wedged a cut piece of old rubber exhaust hanger between the part of the muffler that was hitting and the underbody. Never had a problem after that. And no, the cut piece of rubber exhaust hanger didn't melt at all.

Edit: I'm 90% sure these are the same ones I used. Same color and everything. Lol
https://www.cobbtuning.com/products/...d-individually

 
Rep Power: 0

The noise is coming from where the muffler is, I just don’t know if it could be that simple of an issue. The only reason why is that it just started this week after 4 months. I’ll look at it in the morning, thanks.

 
Rep Power: 512

I was surprised when I found the issue, too, since it seemed to be too stupid to be the culprit. Quick test would be to crawl under rear of car (engine off). Grab muffler and shake. Mostly in up and down motions. Should be able to tell quite easily if/where muffler is hitting underbody.

 
Rep Power: 0

It’s not that... I tapped the muffler and cat with a rubber hammer, it all sounds fine.