Method and apparatus for determining fuel supply amount of internal combustion engine

The amount of a change in the fuel injection amount that needs be made in accordance with a change in the target idle speed NETRG is corrected by the rotation speed correction factor QIPNT. When the engine friction is changed due to a change in the actual engine speed NE, the fuel injection amount is adjusted by using a friction correction factor QIPBB. The friction correction factor QIPBB is obtained independently from the other correction factors and by using a specially designed map. Therefore, all the correction factors are easily computed in accordance with changes in the target idle speed NETRG, which facilitates the development of programs for controlling fuel injection.