What causes cats to clog?
 

I think my cats are clogged. I've been getting a faint smell of rotten eggs lately from my exhaust. Also, I've noticed it doesn't pull as hard as it used to. My car is a 01 z28 a4. It only has 36k miles on it and I always run premium gas. What actually causes them to clog? Also, what makes the smell? I guess I can just remove them or gut them untill I get my lt's. I'm guessing clogged cats reduce gas milleage. In MI they don't do emissions so it wouldn't hurt anything. But would it throw a code? A lot of questions, I know, but thanks for any info.

race gass (leaded gass) will do it... i know i cant spell

cory

I don't think my car has ever seen a drop of race gas.

take the car in. the cats are good for 8 years or 80,000 miles

If you only have 36,000 miles on your car, then the cats are under warranty as an emissions device. Cats can get clogged by excessive heat melting the brick face in places, destroying the cells. Running lean could conceivably do damage, but standard PCM programs have tables built in to add fuel in certain high-heat WOT conditions that should keep the heat from getting that severe.

Removing the cats will cause the PCM to throw a code.

Not positive, but there may be a TSB related to the sulfur smell you're experiencing.

Carbon too.

I have 77.7k on my car, should I be expecting my cat to fail anytime soon???

The smell is definityly coming from the exhaust. Smells exactly like my blazer with a clogged cat did. I just removed it and the smell went away. Maybe I'll just jump on ebay and get some hi flow cats or maybe just wait until I get my LT's.

my cat clogged we believe anyway ....my brother punched it out and my car has been better but not her self since .....i think my opti might be failing....my car has 73000 miles on it and is 9 year old