Abstract: An atmospheric pressure detecting method for controlling an internal combustion engine, which can detect atmospheric pressure and takes the atmospheric pressure as one of control conditions of the internal combustion engine without using a throttle sensor and an atmospheric pressure sensor, is provided; wherein a maximum value and a minimum value of intake pipe pressure generating while the internal combustion engine performs one combustion cycle are detected; wherein an absolute value of a difference between the maximum value and the minimum value of the intake pipe pressure is detected as an intake pipe pressure change quantity; and wherein the maximum value of the intake pipe pressure is taken as a detection value of atmospheric pressure when the intake pipe pressure change quantity is equal to or less than a set value.

Abstract: An operating state detecting method for an internal combustion engine for detecting whether the engine is in an accelerating state and/or whether it is in a decelerating state without detecting the opening degree of a throttle valve is to be provided. A plurality of rotational angle positions of a crankshaft of an internal combustion engine are specified as sampling positions, and pressures within an air intake pipe sampled at each sampling position are stored. Every time a pressure within the air intake pipe is sampled at each sampling position, the newly sampled pressure within the air intake pipe is compared with a previous pressure within the air intake pipe sampled at the same sampling position one combustion cycle before, and whether the engine is in an accelerating state and/or whether it is in a decelerating state is determined from the result of comparison.

Abstract: An intake negative pressure detection apparatus for detecting an intake negative pressure of all cylinders of a multi-cylinder internal combustion engine by using negative pressure sensors, the number of which is fewer than the number of cylinders and each of the negative pressure sensors provided commonly for two cylinders of the internal combustion engine and connected to intake passages of the two cylinders, respectively through a change-over valve, which is so constructed as to introduce a pressure within the intake passage having a higher absolute value of the inner negative pressure among the intake passages into the negative pressure sensor.