PURPOSE: To aim at improvements in fuel consumption, by finding such a crank angle position as making pressure inside a cylinder come to the maximum, while controlling a fuel injection quantity according to frequency that the crank angle position slips off the specified crank angle.

CONSTITUTION: Those of pressure detectors 23W26 are installed in each of cylinders. For each pressure detector, those ones using a piezoelectric element as a washer for ignition plug or using the piezoelectric element for a gasket between a cylinder head and a cylinder block or the like are used. And, a crank angle position θpmax at a time when pressure inside a cylinder comes to the maximum is measured with an operation circuit 30. Such frequency that this crank angle position θpmax slips off the specified crank angle is found, and a fuel injection quantity is thus controlled according to this frequency. With this method, driving a car in economical fuel consumption can be attained in a state of keeping engine combustion up in a stable limit.