Α three Way Catalytic (TWC) converter is used to reduce exhaust emissions. This type of converter can reduce hydrocarbons (HC), carbon monoxide (CO) and oxides of nitrogen (NOx).
The upstream section of the converter contains a reducing/oxidizing bed to reduce NOx while oxidizing HC and CON. Αn air supply pipe from the air injection system injects air between the beds of the converter. Thus the second converter bed oxidizes any remaining HC and CO to efficiently reduce exhaust emissions.
Although most original equipment (OEM) converters are designed for go over 100,000 miles, engine components problems could cause a premature failure. For example phosphorus, which is found in motor oil, can foul the converter if the engine is burning oil due to leaking piston rings or worn out valve guides or rings.
Unburned fuel is probably the most common cause of catalytic converters. Cylinder misfire, due to faulty spark plug or ignition coil, and leaking fuel injector, could cause unburned fuel to enter the catalytic converter. The unburned fuel will cause the catalytic converter to overheat and damage the material inside.
Catalytic converter failures generally fall in the category of physical damage or catalyst failure. Physical damage usually can be visually identified – cracks, dents, etc. Internally, the structure can be cracked, broken, or melted. Where high heat may have lead to catalyst failure, the engine and related systems need to be thoroughly checked.
Unfortunately there no way to repair the catalytic converter and replacement is the only option. Up until the 1995 model year, converters were covered by a 5-year/50,000 mile federal emissions warranty (7 years or 70,000 miles in California). In 1995, the warranty was extended to 8 years or 80,000 miles.