Abstract: Where performing a main injection, and a sub-injection that injects a minute amount of fuel in a short region of driving time, a check is conducted to determine whether or not the minute amount of fuel is injected accurately. In a specific cycle at a time of cold starting when catalyst warm-up control is performed, the main injection is omitted and a checking injection corresponding to a sub-injection is performed. Injection conditions of an in-cylinder injection valve are made uniform between the checking injection and the sub-injection. A fuel amount that is actually injected from the in-cylinder injection valve in the specific cycle is calculated based on an air-fuel ratio of exhaust gas discharged from an engine and an in-cylinder air amount, and is compared with a fuel amount that theoretically should be injected from the in-cylinder injection valve.

Abstract: Where performing a main injection, and a sub-injection that injects a minute amount of fuel in a short region of driving time, a check is conducted to determine whether or not the minute amount of fuel is injected accurately. In a specific cycle at a time of cold starting when catalyst warm-up control is performed, the main injection is omitted and a checking injection corresponding to a sub-injection is performed. Injection conditions of an in-cylinder injection valve are made uniform between the checking injection and the sub-injection. A fuel amount that is actually injected from the in-cylinder injection valve in the specific cycle is calculated based on an air-fuel ratio of exhaust gas discharged from an engine and an in-cylinder air amount, and is compared with a fuel amount that theoretically should be injected from the in-cylinder injection valve.

Abstract: In an internal combustion engine, an ignition plug is arranged near a center of an upper wall surface of a combustion chamber, and is used to ignite air-fuel mixture. Fuel injected from a port fuel injection valve is directed toward the center of the combustion chamber when the intake valve is open. The engine is configured to generate a tumble flow in a cylinder. A flow speed of gas around the ignition plug during ignition is controlled by changing a pattern of tumble flow between an ordinary first tumble flow pattern and a different second tumble flow pattern on the basis of an engine rotation speed. The tumble flow having the second pattern is generated by overlapping a fuel injection period of the port fuel injection valve with the open period of the intake valve.