What is the one of most important emissions control devices on a vehicle today? The catalytic converter, because it helps cleans many exhaust pollutants that exit the engine. It operates at temperatures of 600 to 1000 degrees F.

BTW: Parking over a pile of dry leaves or the like can start a fire..

If the converter does its job efficiently, the vehicle will meet emissions and pass both a tailpipe emissions check with an OBD II emission scanner, a plug-in emissions tester.

The causes of failure that can actually damage an engine to the point of engine replacement basic overheating of all internal engine components thus damaging seals, rings and all hardened parts leading to a failure.

TYPES OF CATS

Before we go any further, we need to take a quick look inside the converter to understand how it operates. Inside the outer shell, which is usually stainless steel, is a ceramic or metallic honeycomb sprayed with a very thin coating of special reactive metals. These metals have the properties needed to ignite the chemical process. They are not used up over time, but become full so to speak over time.

The first converters came out in about 1975 were “two-way” or “oxidizing” converters because the catalyst only reacted with hydrocarbons [HC] and carbon monoxide [CO] in the exhaust.

The power-train control module [PCM] adjusts the air/fuel mixture when the engine is warm by manipulating the rich/lean signal from the oxygen sensor in the header exhaust pipe. By rapidly changing the air/fuel mixture back and forth, the overall mixture averages out and keeps emissions at a minimum.

On some newer vehicles, a new type of oxygen sensor, also called an “air/fuel ratio” sensor) is used. Instead of producing a high or low voltage signal, the signal changes it’s attitude in direct proportion to the amount of oxygen in the exhaust.

This provides a more precise measurement for better fuel control and tells the PCM the exact air/fuel ratio.

I realize this is a complicated article to understand. The most important thing to know is that a clogged cat on any car or truck will inhibit the power and performance dramatically. Possibly cause an engine failure due to heat build up in the engine. I have seen several vehicles, such as a Ford engine needing the be replaced with a used engine due to forcing the vehicle to go when it clearly had a problem and lacked power. 

I have also installed a used Toyota engine in Tundra pickup that had severe cat problems. Read our next post on GotEngines.com Blog, completing your catalytic converter education.