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Catalytic Converter keeps going bad

07-28-2010, 03:20 PM
Hello, just wondering if anyone else has had this problem, and solved it? I have had my 2001 Pontiac grand am since 2003 and since then I have had to replace the catalytic converter about 3 times. Now, the car is reading service lights, had the codes checked today at advanced auto parts and it looks like the converter is going bad AGAIN!

Is there something else that's not working correctly that could be causing the converter to go bad?? as the times are now we seriously can't afford a mechanic shop. We have a good family friend who is a mechanic, but lives about 2 hours away so we rarely see him. Just trying to think of where to begin so I can at least look into fixing the other problems while replacing the converter.

Thanks for any help.


07-28-2010, 06:35 PM
Welcome to AF!!

It is quite unusual for a cat to go bad once let alone four times. You may have issues with the O2 sensors that are allowing the engine to run rich and the extra fuel is causing the cat to burn out. It is also possible that you are getting coolant in the cat from a leak in the head gasket that could cause this. If you know the codes would you please post them so that we can see what is actually happening with the car.

07-28-2010, 11:04 PM
I agree with GTP Dad. A cat ain't supposed to burn out. The 2 usual cause are too much fuel and burning coolant.

The goal of the cat is to burn the unburn/partially burn fuel. Doing so it become hotter. They size up the cat based on the expected fuel to burn. If your O2 sensor is wrong it can let too much fuel in the engine, making it unable to completly burn it, causing the cat to overheat

As for the coolant, I don't have the full explanation, however it seems to be a chemical incompatibility between the coolant and the cat, causing it to get ruined. (but don'T quote me on that, I never did the full research, so it might be something else, but that is what I read somewhere)

If you need to add coolant from time to time then you have a blew up gasket or cracked head or something. If you get bad MPG, well, you would have your answer.

07-29-2010, 04:02 PM
Ok... unfortunately i failed to ask for the codes. I had them read at advanced auto parts. I'll probably take the car there again or elsewhere and try to get those codes written down. Thanks for the explanation and such a quick response.. ill keep yall updated.. this at least points us in a direction to look. I hope its not a head gasket thing... i dunno whats worse though either.

02-27-2018, 12:11 PM
I'm having a problem with my Cat too! I have a Honda Civic 2000 EX that my dad fixed up and played with, and he gave it to me around the beginning of last year. I just got my car back from the shop last week from needing my cat to be replaced again. It's the 5th time now. Luckily it's under warranty but this isn't something that I want to keep happening and I want to nip the cause of it. Every time I ask why the cat has failed, they tell me because it's clogged. I know there are a couple of various reasons as to why it would clog, but it's a bit beyond me right now. I'm sure my repair shop is tired of replacing it multiple times now too, but they're kind of fascinated at the same time since this never really happens. A part of me thinks it's something that my dad did to the car to cause this. Oddly enough, this has never happened to him when he had it. But he knew cars and didn't drive it as often as I do either. Help

Tech II
02-27-2018, 02:41 PM
Why are you in the Grand AM forum?

Main failures of cats are misfires, car not running close to 14.7:1 f/a ratio, bad O2 sensors, cats contaminated, or replacements not up to OEM specs....

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