Failure diagnosis device for an engine which compares airfuel ratio and exhaust pressure with a predetermined value

摘要

A failure diagnosis device for determining engine abnormalities by comparing the air-fuel ratio or the exhaust pressure of an engine with a predetermined value or by determining that the air fuel ratio or the exhaust pressure of the engine is different from the average air-fuel ratio or the average exhaust pressure by a predetermined amount. This comparison is made only when the engine is in a predetermined running condition in which either the air-fuel ratio or the exhaust pressure is stabilized for a predetermined period of time. When the air-fuel ratio or exhaust pressure is different from the average air-fuel ratio or from the average exhaust pressure by a predetermined value, engine abnormality can be detected for each cylinder or for each cylinder group.