Signs That a Catalytic Converter Is Going Bad

Updated April 17, 2017

A catalytic converter is an exhaust emissions device that is part of a vehicle's exhaust system. In charge of lowering the exhaust emissions that exit a vehicle's tail pipe, a catalytic converter can negatively impact vehicle performance if it goes bad or stops working properly. What follows is a brief list of the most common signs of a bad catalytic converter.

Reduced Exhaust Flow

A major sign of a plugged up and/or bad catalytic converter is reduced exhaust flow measured at the vehicle tail pipe. Engine exhaust must travel through a catalytic converter before exiting the tail pipe; a bad catalytic converter can block and/or impede exhaust flow.

Reduced Engine Power

If a bad catalytic converter seriously impedes the flow of a vehicle's engine exhaust flow, reduced engine horsepower can occur. This is due to the increase in engine exhaust back pressure that results whenever engine exhaust flow is impeded and/or reduced.

Reduced Exhaust Pipe Temperature

It is common for a bad and/or plugged catalytic converter to cause abnormally low exhaust pipe temperatures on the backside of a catalytic converter. As engine exhaust exits an engine and travels down the exhaust system and through the catalytic converter, the exiting exhaust flow can be restricted enough to cause significantly reduced exhaust pipe temperatures between the catalytic converter and the tail pipe.

Increased Hydrocarbon Emissions

Catalytic converters work by reducing the levels of hydrocarbon emissions exiting a vehicle's tail pipe. A bad catalytic converter can lose its emissions-lowering capabilities and cause an increase in exhaust hydrocarbon emissions, a condition that is normally picked up when a vehicle is undergoing a routine smog inspection.

Reduced Fuel Economy

Any obstruction and/or abnormality in a vehicle's exhaust system has the potential to reduce vehicle gas mileage by creating exhaust back pressure within a vehicle's engine. A bad catalytic converter can cause a reduction in vehicle fuel economy if it restricts the flow of engine exhaust to the point of causing a marked increase in engine exhaust back pressure.

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