Abnormality detecting apparatus for internal combustion engine

An abnormality detecting apparatus for detecting an abnormality of an internal combustion engine, wherein said engine includes a crankshaft, an intake port, a corresponding intake valve, an exhaust port, and a corresponding exhaust valve, wherein said valves are driven in a predetermined timing relationship with respect to the crankshaft, wherein said intake valve and exhaust valve selectively open or close the intake port and exhaust port, respectively, and the valve timing of at least one of the intake valve and exhaust valve is altered by a variable valve timing mechanism, said abnormality detecting apparatus comprising:

• means for detecting running conditions of the internal combustion engine,
• means for determining a target valve timing of the valve altered by said variable valve timing mechanism in accordance with the running conditions of the engine,
• means for detecting a real valve timing of the valve altered by said variable valve timing mechanism,
• means for controlling said variable valve timing mechanism to change the valve timing of the valve to be altered to converge said detected real valve timing to said determined target valve timing,
• means for detecting generation of abnormality in said variable valve timing mechanism, wherein said abnormality generation detecting means decides that an abnormality has been generated in said variable valve timing mechanism when the absolute difference between said determined target valve timing and detected real valve timing is at least a first predetermined value and an amount of change in said detected real valve timing over a predetermined time is at most a second predetermined value, and
• means for deciding whether said variable valve timing mechanism has recovered to a normal state, wherein said normal recovery deciding means decides that the variable valve timing mechanism has recovered to a normal state when an altered amount of the detected real valve timing over a predetermined time is less than or equal to a third predetermined value after detecting an abnormality of the variable valve timing mechanism.