Exhaust Back Pressure and Emissions

Maintenance/Repairs
1

My 2005 Buick Century with 353k miles gets a recurring P0420 code, catalytic converter operating below efficiency level. Twice this year, I tried using Cataclean, but with no success. I noticed a small hole in my muffler at the seam. Could a lack of exhaust back pressure cause the CC to operate inefficiently or improperly? Can anyone recommend a catalytic converter cleaner? Or, is it all snake oil?

2

No, lack of backpressure has nothing to do with your issue.

You need a new catalytic convertor most likely

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3

the muffler is after the catalytic converter. So a hole in the muffler isn’t going to effect catalytic performance.

I know people go into denial, (and I ain’t talking the river), when this code appears, but in all the years being a mechanic this code always meant the converter needed to be replaced. Especially if the vehicle has over 300,000 miles.

You just need to hook a scanner up and watch what the #2 O2 sensor is showing to confirm if the cat is bad.

Tester

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4

Yeah, likely the cat. How many miles do you go between adding a quart of oil?

5

Well first of all, Cataclean is a product which you add to the fuel, so it gets burned in the engine. There is no chance in heck that this product could actually work to clean a catalytic converter. Assuming that the reason why the cat has lost effectiveness is a buildup of soot, etc. on the catalyst mesh, the only way to clean it is to unbolt and remove it, and clean with carburetor cleaner or a similar solvent. I have done this successfully to get a vehicle through emissions testing, but I suspect that even cleaning will only work for so long.

At over 300,000 miles, I doubt cleaning would work, and assume the cat is worn out. As long as you don’t live in California, you can replace it for a few hundred bucks if you DIY. It should be noted that some states follow California emissions standards, and won’t allow a federal cat to be sent there, however I believe California is the only state where they physically verify that your cat has a C.A.R.B. number etched on it.

6

Tester