Abstract: A fuel control system for an internal combustion engine capable of correcting an inlet air flow rate, used for the computation of a fuel injection, in consideration of a blow-back flow rate. The inlet air flow rate is detected by a hot-wire type sensor and sampled by a control unit. The control unit determines whether or not the sampled inlet air flow rate has reversed twice its gradient from the negative one to the positive one between predetermined crank angles of the engine and computes the blow-back flow rate subtracted from the inlet air flow rate.

Abstract: A fuel injection control apparatus for an internal combustion engine using a hot-wire type air flow sensor wherein, even during a low engine speed and in a fully opened condition of the throttle valve of the engine, the output of the air flow sensor is corrected corresponding to the opening of the throttle valve and the engine speed on the basis on a predetermined relationship therebetween, thereby providing a proper A/F ratio.

Abstract: Opening degree of the throttle valve of an engine is detected and compared with a plurality of throttle opening degree reference values which are preset to be minuter in the lower region of the throttle opening degree. Each time the actual throttle opening degree exceeds one of the reference values, an extra fuel injection pulse is outputted in addition to regular injection pulses to increase the amount of fuel to be supplied to the engine.

Abstract: A method and apparatus for controlling an air-to-fuel ratio of an internal combustion engine in which the air-to-fuel ratio is maintained within a predetermined control width or range even if one or more of the sensors which detect the conditions of the engine necessary to compute the desired air-to-fuel ratio fail. An air flow sensor produces an output signal having a frequency determined in accordance with the air flow rate into the engine, an oxygen sensor disposed in the exhaust manifold of the engine detects whether the air-to-fuel is lean or rich, and a coolant temperature sensor detects the coolant temperature of the engine. Transitions in the output from the oxygen sensor are used to control the integrating direction of an integrator circuit composed of an up/down counter. A predetermined number of integration values are averaged to compute upper and lower limits of the controlled ratio.