Abnormality diagnosing system for internal combustion engine

Abstract

An abnormality diagnosing system for an internal combustion engine including a first fuel injection valve that injects fuel into a cylinder, and a second fuel injection valve that injects fuel into an intake passage is provided which has a control device controls an injection pattern of the first fuel injection valve and the second fuel injection valve. The control device stores engine operating conditions when an abnormality occurs in the engine, and make a return-to-normal determination as to whether the engine returns to a normal operating state when similar operation conditions that are the same as or within predetermined ranges of the stored operating conditions are established. The injection pattern is selected from patterns in which the fuel is injected solely from the first fuel injection valve, solely from the second fuel injection valve, and from both of the first and second fuel injection valves. The control device stores the injection pattern when the abnormality occurs, and makes a return-to-normal determination on condition that the engine is operating in an injection pattern that is the same as the stored injection pattern.