Reasons For Catalytic Converter Failure
These Are Not Defects and Thereby Not Covered Under Warranty
Excess Fuel Entering Exhaust
The fuel that powers your vehicle is meant to burn in the combustion chamber only. Any fuel that leaves the combustion chamber unburned will enter the exhaust system and light-off when it reaches the catalytic converter. This can super-heat the converter far above normal operating conditions and cause a Converter Meltdown. (even if the engine seems to run fine) Possible causes are an incorrect fuel mixture, incorrect timing, defective spark plugs, a faulty oxygen sensor, sticking float, faulty fuel injector or a malfunctioning check valve etc.
Engine Tune Up Needed
A number of problems could occur to the catalytic converter as a result of an engine that is out of tune. Any time an engine is operating outside proper specifications, unnecessary wear and damage may be caused to the catalytic converter as well as the engine itself. The damage is often the result of an incorrect air/fuel mixture, incorrect timing, or misfiring ignition system. (plugs,wires,coil etc.) Any of these conditions could lead to a catalytic converter failure or worse.
Oil or Anti-Freeze Entering the Exhaust
Oil or Antifreeze entering the exhaust system can block the air passages by creating heavy carbon soot that coats the ceramic catalyst. These heavy Carbon Deposits create two problems. First, the carbon deposits prevent the catalytic converter from reducing harmful emission in the exhaust flow. And second, the carbon deposits clog the pores in the ceramic catalyst and block exhaust flow, increasing backpressure and causing heat and exhaust to back up into the engine compartment. Your engine may actually draw burnt exhaust gasses back into the combustion chamber and dilute the efficiency of the next burn cycle. The result is a loss of power and overheated engine components. Possible causes are worn piston rings, faulty valve seals, failed gaskets, or warped engine components.
Oxygen Sensor Not functioning Properly
An oxygen sensor failure can lead to incorrect readings of exhaust gasses. The faulty sensor can cause a too rich or too lean condition. Too rich and the catalyst can melt down. Too lean and the converter is unable to convert the hydrocarbons into safe elements and may not pass an emission inspection.
The ceramic catalyst inside a catalytic converter is made from a light-weight, thin-walled, fragile material. It is protected by a dense, insulating mat. This mat holds the catalyst in place and provides moderate protection against damage. However, road debris striking the converter or improper or a broken exhaust system support can cause a Catalyst Fracture. Once the ceramic catalyst is fractured, the broken pieces become loose and rattle around and break up into smaller pieces. Flow is interrupted and backpressure in the exhaust system increases. This leads to heat build up and loss of power. Possible causes of a catalyst fracture are road debris striking the converter, loose or broken hangers, potholes or off-road driving.