What is the cause of catalytic damage leading to single or multiple cylinder misfires?

[LeJessica]

Multiple cylinder misfires in a car engine are issues related to the ignition system, including problems with the ignition coil and other wiring harnesses, as well as blockages caused by fuel injectors. Generally, the causes of multiple cylinder misfires in a car engine include the following: 1. Ignition failure, which requires checking the ignition coil and high-voltage wires. The ignition coil cannot be repaired and must be replaced if faulty; 2. Fuel injection failure, which may be caused by wiring issues or poor fuel injection pressure; 3. Human operational errors, such as carelessness or mistakes during maintenance: faults caused by disturbances, loose connectors, etc.; 4. Wear and aging, untimely maintenance, or the use of inferior, substandard, or non-compliant engine oil; 5. Engine failure, which requires timely replacement.

[StValerie]

Having driven for over a decade, what I fear most is when catalytic converter issues get tangled up with misfires. Multi-cylinder misfire means several engine cylinders aren't functioning properly, where injected fuel gets expelled unburned. This unburned fuel-air mixture rushes into the exhaust pipe, and since the three-way catalytic converter already operates at high temperatures, encountering these fuel vapors causes intense combustion. The extreme heat directly damages the honeycomb structure inside the converter. Conversely, a clogged catalytic converter can also trigger misfires - restricted exhaust flow is like holding one's breath, causing the engine to suffocate and operate erratically. Common causes include worn spark plugs, faulty ignition coils, or clogged fuel injectors. If you notice severe shaking, poor acceleration, or the check engine light comes on, don't push it - get to a professional shop immediately to read trouble codes. Replacing a catalytic converter isn't cheap. Remember to regularly change spark plugs and use certified fuel additives to clean the fuel system, preventing minor issues from becoming major problems.

[DiNevaeh]

Last week, my car suddenly started jerking and shaking during acceleration, with the engine malfunction light flashing. Diagnostics revealed that the third cylinder's spark plug electrode had melted, causing a misfire, and the catalytic converter was also burnt and deformed. The mechanic explained that unburned fuel mixture from the misfiring cylinder ignited a secondary combustion inside the catalytic converter, spiking temperatures to over a thousand degrees and instantly melting the fragile ceramic substrate. This issue is particularly common in older vehicles, as issues like ignition coil leakage or fuel injector carbon buildup can lead to incomplete combustion. A damaged catalytic converter, in turn, causes exhaust system blockage, forcing the engine to work harder, creating a vicious cycle where more cylinders may fail. To fix this, the root cause of the misfire must be addressed first—such as replacing the faulty ignition coil—before tackling the clogged exhaust system. It’s recommended to check spark plug gaps monthly and monitor for abnormal engine vibrations during cold starts to prevent such issues proactively.

[SanJaxson]

The relationship between the catalytic converter and misfire is like a domino effect. Worn spark plug electrodes or cracked ignition coils can cause a cylinder to misfire, while fuel injection continues as usual. Large amounts of unburned gasoline rush into the catalytic converter, where they undergo intense oxidation and release heat under high-temperature catalytic conditions, rapidly degrading the precious metal coating inside and causing the substrate to melt or even crack. At this point, the engine may experience abnormal operation in multiple cylinders due to increased exhaust backpressure. I often recommend two basic checks to car owners: using a multimeter to measure if the coil resistance exceeds normal values and inspecting spark plug carbon buildup with a borescope. If the temperature at the front end of the catalytic converter rises abnormally, it's a cause for concern. Repairs should address the root cause: replacing blown fuses or aging sensors, then assessing whether the catalytic converter needs replacement. Regularly using a diagnostic tool to read OBD data streams can help avoid overly rich air-fuel mixtures.