Avenir

There is a glitch in the computer program to control the engine, and therefore, (1) when the vehicle slows down during high-speed driving, the fuel that was not burnt due to lack of air may be burnt at the front catalysts, or (2) uneven exhaust air flow inside the exhaust manifold may cause the inside of the front catalysts to heat up partially. As a result of these, the front catalysts may be damaged from inside due to heat degradation resulting from the repeated exposure to heat at a high temperature.

On certain vehicles, the engine cylinder block can crack from a high engine load because it is defective in manufacturing (casting). If this occurs, the combustion gas can enter the coolant passage inside the cylinder block, in which case the coolant could fail to circulate properly, resulting in overheating.