What could cause a catalytic converter to clog?

Dear Car Talk

Dear Car Talk | Feb 01, 1993

Dear Tom and Ray:

I have a 1987 Thunderbird with approximately 80,000 miles on it. I was driving on the expressway going about 65 mph, when I pressed on the gas pedal and lost power. I had the car towed, and my mechanic told me I needed a new catalytic converter because mine was clogged. I paid $285 for the new converter, and now the car is running fine. What could have caused the converter to clog? I use only 89 octane brand-name gas.

TOM: Well, Kev, converters can plug up for the same reason that Michael Jackson wears one glove. That is, for NO apparent reason. Actually, they just slowly disintegrate over time and plug themselves up.

RAY: The EPA currently mandates that manufacturers warranty catalytic converters for 50,000 miles. So you almost never see them plug up before that. And even 80,000 is a little on the early side.

TOM: So your mechanic should not necessarily assume that the converter died a natural death. It's possible that something's wrong with the engine. If the fuel mixture is too rich--because of faulty injectors, for example--that would produce excess carbon, which could plug up the converter.

RAY: Or if the emission control system is malfunctioning, and the air pump isn't working properly, that could also plug it up.

TOM: And if one of these things IS wrong, your brand new converter will be junk before long, too.

RAY: So go back and ask your mechanic to check the tailpipe emissions. If they're OK, then you can relax. Your converter should last another 80,000 miles...or about 40,000 longer than the rest of the car.

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