What does a catalytic converter do?

Catalytic converters are a key component of automotive emissions control systems, reducing the amount of pollutants emitted from the tailpipe. They convert hydrocarbons, carbon monoxide and nitrogen oxides (hazardous substances) into oxygen, nitrogen and carbon dioxide.

Mufflers and Catalytic Converters

Muffler and Catalytic Converter: The muffler is on the left and the catalytic converter is on the right.

What does a catalytic converter look like?

The exact design varies between manufacturers, but catalytic converters generally look like mufflers and can be oval or cylindrical.

Where is the three-way catalytic converter located in the car?

The catalytic converter is part of the exhaust system. They are located between the engine and the muffler, usually closer to the engine. This helps them heat up quickly to the high temperature they are most effective at.

Most of the pollutants emitted by modern vehicles occur in the first few minutes after a cold start, before the engine and catalytic converter reach their optimal temperature.

inside the catalytic converter

What's inside a catalytic converter?

Inside a catalytic converter there is usually a piece of ceramic coated with various precious metals, including palladium, rhodium and platinum. These are "catalysts" that create chemical reactions that convert harmful gases into safer substances.

The ceramic sheets in catalytic converters often look like honeycombs. It's shaped so that gas can flow through it more easily.

How does a catalytic converter work?

Catalytic converters are critical emission control devices. Vehicle exhaust contains a variety of harmful gases, including carbon monoxide (CO), nitrogen oxides (NOx), and volatile organic compounds (VOCs)/hydrocarbons. Catalytic converters use palladium, rhodium and platinum to create a chemical reaction that reduces these gases. The catalytic converter releases carbon dioxide along with harmless oxygen and nitrogen. Carbon dioxide is a greenhouse gas that contributes to global warming, but it is less harmful than carbon monoxide, nitrogen oxides and volatile organic compounds, which cause smog and acid rain and can cause human health problems.

Which cars have catalytic converters?

All modern vehicles with internal combustion engines are equipped with catalytic converters. Catalytic converters have been required on new cars since 1975, so very old vehicles don't have them. Electric cars don't need catalytic converters because they don't have exhaust systems.

Are there different types of catalytic converters?

Yes. The type of automotive catalytic converter may depend on:

car size

Is it a hybrid (hybrid engines don't run as hot, which affects how the catalytic converter operates)

where the catalytic converter is located

catalyst used

Whether the converter is approved in California (CARB Approved) or nationwide (EPA Approved)

The age of the car (very old cars have two-way catalytic converters; newer cars have three-way catalytic converters)

Catalyst structure (honeycomb or ceramic beads)

Frequently Asked Questions about Catalytic Converters

Catalytic converter problems are fairly common and expensive to fix. The following are the most likely problems.

overheat

The catalytic converter can overheat when excess unburned gas passes through the exhaust pipe due to a misfiring spark plug, leaking exhaust valve, or other fuel system problems. A faulty oxygen sensor can also cause overheating. The oxygen sensor monitors the amount of oxygen in the exhaust and tells the engine computer how to adjust the air-fuel mixture. When the oxygen sensor stops sending a signal, the computer gets confused and the air-fuel mixture can become too "rich," meaning it has too much gas in it. Overheating can damage the engine, reduce performance, and often trigger the check engine light.

jam

Catalytic converters can also become clogged with carbon buildup over time. Oil and engine coolant can also clog the catalytic converter and restrict the flow of exhaust gases. When the exhaust restricts the amount of gas that goes out, less air gets into the engine, causing slow acceleration or stalling. A clogged or damaged "cat" can smell like rotten eggs or sulfur, and can create excessive heat under the vehicle.

external damage

Converters are usually hidden away from road hazards, but on some vehicles they can be damaged by debris.

Stolen catalytic converter

One of the most common catalytic converter problems is a stolen catalytic converter. Since catalytic converters contain precious metals, they are one of the most commonly stolen auto parts.

Cars most often targeted by catalytic converter thieves

Inside of a damaged catalytic converter

Did you clean or unclog your catalytic converter?

Most automakers and mechanics do not recommend cleaning catalytic converters. Still, there are several cleaning products that claim to clear clogs. Add the solution to the tank and it will work its way through the engine and exhaust. These products may be able to reduce minor clogging so the check engine light does not come on, or there is no noticeable loss of acceleration. However, they are less likely to clear severe blockages.

Some mechanics recommend removing the converter and soaking it in degreaser and water to clear the clog, while others believe that varnish thinner will do the trick. Neither method is likely to restore the performance of a failed converter to the same state as a new converter.

Are Catalytic Converter Cleaning Products Worth Trying?

Before you spend hundreds of dollars or more on a new converter, these inexpensive cleaning products might be worth a try. But if a qualified technician diagnoses the catalytic converter as severely clogged or damaged from overheating, there's no magic bullet that can fix it. Converter should be replaced.

How much is the three-way catalytic converter?

Prices for catalytic converters range from less than $1,000 in mainstream vehicles to $3,000 or more in some luxury vehicles and expensive sports cars. The average cost is between $1,800 and $2,000. In most cases, the new "cat" will account for most of the cost, since removing the old "cat" only requires loosening a few bolts. However, this is the best case scenario.

Rust can make removing a catalytic converter extremely difficult. On some vehicles, the "cat" may be difficult to reach or require other parts to be removed first, adding to labor costs. Some converters are soldered together and require more work - and more money out of your pocket.

How long is the service life of the three-way catalytic converter?

Catalytic converters typically have a service life of at least 10 years. Many people who have owned cars for an extended period of time have never had to replace one.

However, in addition to the above issues, corrosion, bad gas contamination, repeated short trips that don't allow the "cat" to reach maximum temperatures (allowing moisture to accumulate, creating rust), and other factors can shorten life expectancy.

Can you drive without a catalytic converter?

No, it is illegal to drive without a catalytic converter.