Patent ID: 8261721

Claim:
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, comprising: a control device that controls an injection pattern of the first fuel injection valve and the second fuel injection valve, said control device being configured to store engine operating conditions of an engine speed, an engine load and an engine coolant temperature when an abnormality occurs in the internal combustion 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 engine operating conditions are established, wherein the injection pattern is selected from a first pattern in which the fuel is injected solely from the first fuel injection valve, a second pattern in which the fuel is injected solely from the second fuel injection valve, and a third pattern in which the fuel is injected from both of the first fuel injection valve and the second fuel injection valve; and 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.