I've searched through the 150+ threads on Catalytic Converters, but none really explained my question.

Only question I have is this.

All the threads stated that once the "honeycomb" part on the inside goes bad, it breaks apart and starts rattling in there. I do here a rattle from the underside of the vehicle and do think it's my cat. I say this due to the fact that I'm getting pretty bad gas mileage. I can barely break 300 miles per tank with a combo of city and highway driving without pushing it, at any time.

BTW, this is on a bone stock D15B7.

All the threads I've read also stated once that "honeycomb" breaks apart, your cat beomes clogged and your gas mileage drops. Again, read above.

I have 137,xxx miles. So, I'm aiming more to the point that my cat is definitely clogged/shot.

I've also read that cats break down even more due to your engine running rich. My timing is up to spec, checked 3 times.

So, my question is, do catalytic converters break down over time/miles/age. Or do they break down ONLY due to your engine running too rich?

Thank you.

 

Cats can and do certainly break-down over time, so there's a chance that perhaps your cat is at the end of its life cycle. If should be easy enough to inspect the cat once you remove it, and if the failure was due to an overly-rich condition (which I doubt was the case, unless another component such as the O2 sensor, fuel regulator, etc. is malfunctioning) you should be able to confirm it by the condition of the media. A failure due to a rich condition would eventually cause the media to have a more melted appearance rather than just being broken. Here's a pretty decent guide to cat failure that you might want to check out as well: http://car-sound.com/04failures.asp


Modified by Padawan at 12:09 PM 1/9/2005

 

way the **** up Padawan. Couldn't have said it any better myself.

They certianly do just "die" over time.

 

My cat started rattling like a bitch and I only had 1 year on it. (Hiflo cat) I running rich and I don't wanna say that's what caused it but that's what happened. You could hit the side of the cat and here something rattling inside of it. When I replaced it....The cat wasn't melted is was more brittle and ashey.

 

Thanks for all the information guys. Pretty much answered my question, nailed it right on the head. Just wanted to make sure it's time for it to go and not a worse problem.