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Basics Of Your Vehicle’s Catalytic Converter

Your car’s engine produces exhaust gases as the result of its 4-stroke combustion process. The gases flow from the combustion chamber through each cylinder’s exhaust valve, and make their way toward your vehicle’s tailpipe. Along that path lies the catalytic converter. Its job is to prevent specific elements within the exhaust gas from emitting from the tailpipe. These elements include hydrocarbons (HC), carbon monoxide (CO), and nitrogen compounds (NOx).

Emission standards require that such pollutants are removed from the exhaust. As long as your cat converter is working properly, your car should have no problem passing your state’s emissions test. On the other hand, the cat can become clogged for a number of reasons. If that happens, you might experience a lack of engine power, lower fuel economy, and stalling.

In this article, I’ll describe how the catalytic converter works and explain the factors that can cause it to fail.

How The Component Works

If your engine is running cleanly (i.e. it is not burning oil), the exhaust coming from the combustion chamber should contain very few hydrocarbon and carbon monoxide emissions. In other words, the cat shouldn’t have much to do. Over time, the efficiency of your engine will decline. It will burn less cleanly and the level of HC and CO in the exhaust will rise.

Within your catalytic converter is a ceramic honeycomb. It is covered with special compounds that react to the presence of the exhaust. This reaction causes the molecules in the compounds to hold onto the hydrocarbons, carbon monoxide, and nitrogen compounds, thereby preventing their release into the atmosphere. In doing so, your cat is able to convert otherwise harmful emissions into near-harmless elements, such as nitrogen and carbon dioxide.

Reasons They Fail

The more pollutants that are present in the exhaust, the harder your catalytic converter needs to work. The harder it works, the hotter it becomes. The most common reason cat converters fail is because they become clogged and overheat. The underlying cause of the clog needs to be addressed in order to prevent a replacement cat from clogging.

For example, if your vehicle’s spark plugs become fouled, misfiring can occur. If the exhaust valve fails and causes a leak in a cylinder’s compression, unburned gas can pass into the exhaust system. If an oxygen sensor fails, causing the air-fuel mixture to be too rich, your cat can melt. This can cause an obstruction that leads to a backpressure problem. The result is a stalled engine.

Normally, this component begins operating between 400 and 600 degrees Fahrenheit. This is called its light off temperature. The temperature usually climbs to approximately 1,600 degrees. If the component is forced to work too hard, the temperature can climb to over 2,000 degrees, causing the ceramic honeycomb to weaken. Severe problems usually follow.

If you suspect the level of emissions coming from your engine is too high, have your mechanic check whether your catalytic converter needs to be replaced. Otherwise, you may experience costly engine problems down the road.

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