The Clean Air Act of 1990 regulates 187 different air pollutants and requires all vehicles to be built with a catalytic converter. While this device has done a great deal to reduce harmful emissions, it is not an essential part of the car's operation.
A catalytic converter converts the harmful exhaust gases produced by the car's engine into carbon dioxide and water vapor using catalysts. The car is still creating pollution, but the overall harmfulness of the vehicle's emissions is reduced through the installation of a catalytic converter.
While the converter is not essential to the functioning of the car's basic operations, it is needed to pass an emissions test. A car that does not pass its emissions test is no longer street legal.
While cars without a catalytic converter continue to run, a catalytic converter that is clogged will back up heat and exhaust into the engine. This could cause the engine to overheat if left unchecked.
