Anybody here every have a clogged catalytic converter?

What are the characteristics?

My car, a 2005 Impreza, was running like shit last week. It was raining hard and often here in Minnesota, and the car acted as if there was water in the gas tank.

However, I bring it to a high-pressure car wash on a regular basis, and I've never had the problem before.

So I put a bottle of gas-tank trying stuff in the fuel but it doesn't seem to help. Next, my roommate plugged in his error-code computer into my car's OBD. The trouble codes said cylinder misfires and some kind of problem with the first catalytic converter.

So I pulled off the spark plug wires and re-tighened my plugs. I found one of them to be loose, which I guess might explain shitty performance and that weird thrumming sound my engine was making.

Now my car runs fine (so far... not much of a baseline to work with) but the engine is not at full power. It runs smoothly, there is no loss of gas mileage... but it feels like I've lost about 50 ponies. It takes about a minute to go from 70 to 90 on the highway with the accelerator floored and the car in 5th gear... used to only take a few seconds.

So I'm wondering if my catalytic converter is clogged. I replaced the air filter about three weeks ago.

If it's clogged, how can I fix it? Will banging on it with a rubber hammer help? Do I really have to take the damn thing apart?


And can overfilling your car with oil cause catalytic converted clogging?

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The engine will run just fine at lower speeds, but it has to use more gas/horsepower to push the exhaust gases out.

IF the converter is clogged, it must be replaced, or eliminated.

Some places sell "test pipes" to replace the converter, but then this also makes the car's emissions non-compliant. I know some people simply take the converter off, punch or torch a hole straight through it, and put it back on. The previous methods are NOT legal, but commonplace up here . . .

If your gas mileage has NOT decreased, I would look elsewhere for the loss of power problem before replacing/modifying the catalytic.

Of course, if the test pipe is available - installed, and your performance returns - then you can go ahead and replace the converter(which ain't cheap) and keep it legal.

P.S. - I am an inter-provincially licensed Auto Technician since 1975

But the baselines is only a few hundred miles.


The codereader brought up "Code 420" from the OBD computer, if that helps any.


I wonder if this could be fixed under warranty. I think my car is covered to 60,000 miles for the powertrain and I have a bit more than 50,000 on it right now.

I had a 'Vette that I had a buddy hollow out my cats for me when they clogged up. Yeah, I know...I'm an environmental ass. :eyes:

ANYway, it ran (and sounded) a lot better. Still passed the sniffer test, too (MA inspection).

Our air is so clean we don't need inspections. All the shit in the air blows towards New England... :evilgrin:

All of them. I had woodchip looking crap flow out of mine when I did.

I'm not an enviromental activist, but...


I'm hoping that some kind of solvent can be used to clean them out. Acetone or ammonia or something.


Besides, there's the possibility it's still under warrantly, in which case I can get them replaced.

Matter of fact, my car still passed the sniffer blowing a near zero perfect emission.

If your Subie is an '05, they're still under warranty. I think all car manufacturers have to offer 10 year emissions warranties.

:scared: