Catalytic Converter Repair

What a catalytic converter does

Nearly every street-legal vehicle built in the past several decades has at least one, and many luxury cars have two or more. The converter burns off harmful unburned particles in the exhaust and reduces nitrogen oxides, turning pollutants into water vapor, carbon dioxide, and nitrogen. It reaches an operating temperature of 500 to 1200 degrees F to do it.

The catalyst inside is made of precious metals such as platinum, rhodium, or palladium, which is why thieves sometimes target them.

Signs of a failing converter

• Check engine light
• Loss of power or a rough-running engine
• A rotten egg smell from the exhaust
• Poorer fuel economy
• Backfiring or misfiring

What happens if it clogs

If the converter becomes completely clogged, the check engine light may flash, usually from misfires, and the engine may stall or refuse to start. In extreme cases, excess back pressure can damage the engine internally. A vehicle with a failed converter will also fail a smog check, which means it cannot be registered.

Repair and prevention

A converter usually fails for a reason, such as a misfire or an oil or coolant leak. We find that cause before replacing it, so the new one does not fail the same way.

Replacement is labor-intensive and often requires cutting or welding, so it is not a job to do at home. The oxygen sensors may need replacing at the same time.

Frequent short trips can keep the converter from heating enough, which can lead to clogging. An occasional highway drive of 15 minutes or more helps burn off deposits. Bring symptoms to the shop of your choice.