04 5AT, 131k...

What are the symptoms of clogged cats? I have this odd sound when warmed up... kind of like a rattling (not heat shield). Almost like there's 100 ball bearings rolling around... mixed with a good bit of "fart." The sound only exists at low RPM, and only through first gear, and goes away about mid-way through second gear. It's not tranny, it "goes" fine. Car doesn't run like garbage, but is definitely lacking some power, and doesn't have smooth power through the entire band... just lacking a bit.

No codes, no SES. Wouldn't a clogged cat throw a O2 code.

I'll get it checked out at a muffler shop, just wondering if this seems like symptoms of cats?

 

I'm in the same boat. I'm contemplating to actually mod my 03 sedan 5at because of this....

I noticed when I give it 100% throttle the exhaust smells. Also when I had my buddy on my rear bumper (05 sti) and I was at 100% throttle, I noticed smoke in his headlights. It seemed a lot worse than it really was. My bud said it wasn't bad but it was obvious signs of clogged cats.

Now I'm wondering to just replace the cats with HFC's or test pipes?! But I also would do a full exhaust if I'm at it. When you do HFC/test pipes and add Y pipe and exhaust, it gets really raspy. Now I'm debating to just gut the cats and do Megan Y pipe back..........

GL