Rick's Free Auto Repair Advice

How to save a catalytic converter

Can I save my catalytic converter

If you’ve got a bad catalytic converter, your first thought is that it’s going to cost a lot to replace it. This article shows you how to save a catalytic converter

Many things can cause a catalytic converter to go bad—engine misfires, oil leaking into the exhaust, antifreeze leaking into the exhaust, rich fuel mixtures, etc.

For a better understanding of how a catalytic converter works, read this article

Check out the upstream oxygen sensor

Keep in mind that the job of the upstream oxygen sensor is to tell the computer how well it did in calculating the air/fuel mixture. The job of the downstream oxygen sensor (after the catalytic converter) is to tell the computer how well the converter burned off the excess fuel.

In a normal engine with no misfiring or air/fuel problems, the driver is constantly making minor changes to the throttle and the computer is constantly making corrections to the air/fuel mixture to compensate for driver changes as well as changes in engine power as the vehicle goes up a grade or down a slope. All through this, the upstream oxygen sensor is providing feedback to the computer in the form of a switching signal as it detects a rich/lean condition. This rapid switching is called cross-counting and the upstream sensor should cross-count 8-10 times per second. As an oxygen sensor ages, its ability to detect the rapid changes slows down. So a lazy oxygen sensor can actually damage a catalytic converter by not providing timely information to the computer.

For a better understanding of how an oxygen sensor works, read this article

That can result in a P0420 catalytic converter efficiency code. If you’ve replaced the oxygen sensor, fixed a vacuum leak, replaced a misfiring spark plug, spark plug wire or coil, or fixed a rich fuel condition and still have a P0420 code, AND the catalytic converter isn’t completely plugged, the is one last ditch technique you can try to force the catalytic converter back into proper operation. See this post on how to check if your catalytic converter is plugged.

In a P0420 condition, the downstream oxygen sensor is switching between rich and lean because the catalytic converter isn’t doing its job of removing excess fuel. Here’s one way to force it back into operating condition:

What we’re doing here is deliberately causing a misfire to load the

Overheated catalytic converter

Overheated catalytic converter

catalytic converter with excess fuel to get it into full reaction model and heat it up and burn off any buildup.

Warm up the engine. Remove a spark plug wire and ground it. Run the engine for three minutes at 3000 rpm. Then turn off the engine, reconnect the plug, and take the vehicle out on the highway to blow out any remaining debris. Clear the trouble codes and drive the vehicle. If the procedure works, you’ve saved the cost of a new converter. If it didn’t work, you’re no worse off. In that case, you’ll have to replace the catalytic converter. For more information on which catalytic converter to buy, see this post.

©, 2014 Rick Muscoplat


Posted on by Rick Muscoplat

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