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Short life replacement Catalytic Converter in 2000 Protege

The verification test between the front and back O2 sensors indicates our 14 month old replacement “Cat” is no longer doing it’s job. The “Cat” warranty has 2000 miles left on it. The O2 sensors were replaced at the same time as the “Cat”. The oil was unucharacteristically low on the stick so I fear the “Cat” was getting overloaded but it seems to have happened too fast for that. The first “Cat” went 190,457 miles, we are at 213,161 now. How do I proceed, what are the tradeoffs and alternatives. (the first replacement with labor cost $713.00).

(a note to other Protege owners: the first O2 sensors were probably good as the new ones shortly gave the same error codes. The mechanic then discovered that the exhaust manifold had a crack in it, which turned out to be two cracks and this was complicating the interaction of the sensors with the computer. He arranged for me to pick up a used manifold from a regional/nationally reputable salvage yard. At said yard I inspected the replacement to discover it was also cracked. 20 minutes later they managed to find a good one. The counter man out of curiosity checked his records and found they had sold 23 of these in one year. It turns out the weight of the “Cat” which attaches to the manifold is too much for it. )

Well, it seems that with 2000 miles left on the warranty, then you go ahead and replace the cat. When the existing cat comes off a knowledgeable person may be able to look at it for signs of issues.

If you are burning a bunch of oil that can kill a cat. Your first 190K miles are not relevant. Chances are you weren’t burning as much oil then as you are now.

If this was an aftermarket/universal type of cat that was installed it also is likely not near the quality of the OEM.

So anyway, the thing is under warranty. What is your question? Should someone be checking for cat-killing issues? Yes.

Thank you for responding. It looks like I gave too much overview and not enough pertinent detail. The mechanic who installed the “Cat” formerly worked for a local Mazda Dealer and went out on his own a couple years before it closed it’s doors. He explained to me that the original “cat” was designed to just survive the new car warranty but that a dealer replacement would have a shorter life than the original and would be very expensive. He found the alternative at NAPA.
I am not sure if the warranty will cover if the replacement turns out to have simply fouled from an excessive flood of hydocarbons. (coating the catalysts rendering them ineffective) I have just read a claim by one “cat” manufacturer that their “cat” exceeds OEM and uses a catalyst substrate etc. that is superior to the “universal” catalyst that most replacement “cats” use. That gives weight to your advice about differences in quality.
The car was the last diagnostic job of the day last friday and we needed it back so “cat” killing issues have not yet been pursued. I’m trying to be an informed customer before finding myself faced with an on the spot hurried decision when I take it back in. Again, thank you for contributing “Cigroller”.

I don’t believe that the catalytic converters are designed to just last past the warranty period of 8 years or 80,000 miles. To last that long, they are typically built fairly robust. Absent any stress on the cat, they can and do way out-last even long-term ownership. The 4 on my Ford Explorer are 11 years old with 206,000 miles on them. The one for my Toyota Supra is 22 years old and has 258,000 miles on it.

To have another cat failure before the warranty is out means the cat had a flaw in it, or your car is stressing the cat to the point of early failure. When the cat is pulled from the car, the condition of the substrate can be assessed and the type of stress that it is under can lead to a solution. It’s under warranty, so have them pull it and test it.

As for the cracked manifold, a bad design typically leads to a common failure. If the weight of the cat is to blame for the manifold cracking, the cat can be supported with an addition of a simple muffler strap. I’d be surprised if the shop didn’t already do something while they were working on it.

I can’t say as I buy your mechanics explanation about the converter being designed to just make it through the warranty period and any replacement Mazda OEM converter would not last as long as the original. Both premises are ridiculous in my opinion but he is correct about their being more expensive than aftermarket converters.

Thank you for your contribution BustedKnuckles.

I noticed there are some targeted adds on this site. In particular, suprise, suprise, Catalytic converters. Is it legal for me to buy online a reputable Cat and replace it myself, here in the State of Idaho?

I am a machinist so I am probably one of those to whom applies “a little bit of knowlege is a dangerous thing” if I attempt it myself. I know doing it oneself doesn’t get much warranty coverage. I am expecting the warranty on the present Cat to be of little use, but hope to be pleasantly surprised.