Overheated Catalytic Converter
There are many conditions that can cause a catalytic converter to overheat and fail. The most common cause is unburned fuel entering the catalytic converter. Notice that each of these conditions have one thing in common. They result in unburned fuel entering the exhaust stream. This is because the most likely and common cause for a clogged or damaged catalytic converter is excess unburned fuel (HC) in the exhaust.
Fuel Injectors: Leaking or dripping fuel injectors will result in unburned fuel entering and burning in the catalytic converter. The will result in burning and melting of the substrate. A clogged fuel injector will result in lean burn. Lean burn occurs when there is more air than fuel in the combustion chamber. This results in a misfire and excess hydrocarbons entering and burning in the catalytic converter.
Misfire: Anything that causes a misfire or excess hydrocarbons HC in the exhaust will result in catalytic converter overheating. Check the distributor, spark plug wires, and spark plugs in distributor ignition systems. Check the coil assembly, spark plug, associated wiring, and PCM in today's distributorless and COP ignition systems.
Oxygen Sensors: An oxygen sensor collects information regarding oxygen content in the exhaust stream and sends it to the PCM. This is used to adjust fuel trim. If the oxygen sensor is faulty and sending a signal informing the PCM to enrich the fuel trim a rich fuel mixture will result.
* This question reminds us that a misfiring engine will result in an overheated catalytic converter. Please take note that high fuel pressure not low volume would most likely result in a high concentration of HC in the exhaust.
