PURPOSE: To prevent an engine from overheating without entailing any drop in an engine output, by decreasing the quantity of fuel injection, while quickening the injection timing when temperature in an engine coolant exceeds the reference one.

CONSTITUTION: A steps S2 and S3, those of fuel injection quantity Q and injection timing TI are to be found with engine speed NE and accelerator opening ACC employed. When a coolant temperature TC reaches a reference temperature TR at a step S5, the fuel injection quantity is decreased as from Q1 to Q2, while the injection timing is advanced as from β1 to β2. With this way, the coolant temperature TC can be more dropped than the reference temperature TR so that overheating is preventable.