* Insufficient Fuel/Air Mixture: A rich fuel mixture (too much fuel relative to air) leads to incomplete combustion. Unburnt fuel enters the catalytic converter and ignites, generating excessive heat. This is often caused by issues with:
* Fuel injectors: Clogged or malfunctioning injectors can deliver too much fuel.
* Mass airflow sensor (MAF sensor): A faulty MAF sensor provides inaccurate air readings to the engine's computer, leading to an incorrect fuel mixture.
* Oxygen sensor(s): Bad oxygen sensors provide inaccurate information about the exhaust oxygen levels, causing the engine to run rich.
* Throttle position sensor (TPS): A malfunctioning TPS can also contribute to an incorrect fuel mixture.
* Blocked Catalytic Converter: A partially or fully blocked converter restricts exhaust flow. This causes exhaust gases to build up and heat up excessively. This can be due to:
* Catalyst material degradation: Over time, the catalytic material breaks down, reducing its efficiency and potentially causing blockages.
* Internal damage: For example, a broken honeycomb structure within the converter.
* Ignition Problems: Misfires in the engine cylinders can allow unburnt fuel to enter the catalytic converter, leading to combustion and extreme heat. This can be due to:
* Spark plugs: Worn, fouled, or damaged spark plugs.
* Ignition wires: Damaged or worn ignition wires.
* Ignition coil: A malfunctioning ignition coil.
* Exhaust System Leaks: Leaks before the catalytic converter can allow unburnt fuel and oxygen to mix in the converter, leading to combustion and overheating.
Never touch a red-hot catalytic converter. It can cause severe burns. If you see this happening, immediately turn off the engine and have it towed to a qualified mechanic for diagnosis and repair. Ignoring the problem can lead to further damage to the exhaust system, engine, and even a fire. The underlying cause needs to be addressed, not just the converter itself.
