I recently replaced the stock cat with a magnaflow #94035. The stock cat was working properly since I purchased the car used with 136,000 miles on it. I replaced the cat at around 168,000 miles. The cat went bad in less than 20,000 miles! Granted I had the ignition module go bad, which flooded 3 cylinders with fuel. I had to drive it a little ways, sounded like a flat 4. The muffler shop that I had replace the cat said that the 94035 wasn't legal for Cali. So I payed the $320 to have it replaced with the CARB legal unit. Now, less than 5,000(5 months) later that cat is rattling! I have always had an intermittent CEL for the 2nd o2 bu my mechanic tested the voltage on it and it was fine. Then, more recently I had multiple CEL's for the cam and crank sensors which caused my car to run like crud. The CEL's come and go randomly. Could this have caused the cat to go bad? Also, if the car is burning oil, would that clog the cat? Thanks for any help in figuring this out.

Well, I do know that having excess oil in the pan, which would lead the car to burn a little bit due to it being slightly overfilled, can cause cats to go bad so basically yes on that one. Can't really help you with the rest of the issue though.

Should I be skeptical about the fuel additives that say they can unclog the cat?

i just used a fuel cleaner on my cat cause i was throwing a CEL for the 2nd o2 sensor....

so i reset the code and poured that bottle in.....now i wait



- Cameron (CaliforniaCavalier)
- www.csc-motorsports.com

Well, I tried the guaranteed to pass fuel additive for 2 tanks and the CEL finally turned off and the cat has stopped rattling. It still buzzes a little bit so I will try it for one more tank. I thought people would be interested in knowing if it works. Well, it seems to.