Abstract: A control system for an internal combustion engine where when the engine is decelerating the amount of intake air supplied to a combustion chamber is controlled. A target auxiliary intake air amount SAIRCMD necessary for preventing misfiring of the engine by supplying only an auxiliary intake air amount to a combustion chamber and a target intake air amount GAIRCMD which is a target value of the amount of intake air supplied to the combustion chamber are calculated according to the state NE, AP of the engine. When the engine is decelerating, and misfires, misfire avoidance control is executed controlling an auxiliary intake air amount control valve to be more opened such that the auxiliary intake air amount becomes the target auxiliary intake air amount SAIRCMD and a throttle valve to be more closed such that the amount of intake air supplied to the combustion chamber becomes the target intake air amount GAIRCMD.

Abstract: An fuel supply amount control system for an internal combustion engine comprises an evaporative fuel passage extending between the fuel tank and the intake system of the engine, and a control valve arranged across the evaporative fuel passage, for opening and closing the evaporative fuel passage. A pressure sensor detects pressure within the fuel tank. The opening of the control valve is controlled such that the interior of the fuel tank is held under negative pressure. After termination of negative pressurization of the fuel tank, the amount of fuel supplied to the engine is increased according to an amount of increase in the pressure within the fuel tank detected by the pressure sensor.

Abstract: An evaporative emission control system for an internal combustion engine includes of an evaporative fuel passage extending between the fuel tank and the intake system of the engine, and a control valve arranged across the evaporative fuel passage for opening and closing the evaporative fuel passage. The opening of the control valve is controlled such that the interior of the fuel tank is under negative pressure during operation and stoppage of the engine. The opening of the control valve is set to a desired value according to operating conditions of the engine.

Abstract: An evaporative emission control system for an internal combustion engine includes an evaporative fuel passage extending between the intake system and the fuel tank of the engine. A control valve is arranged across the evaporative fuel passage, for opening and closing the evaporative fuel passage. The opening of the control valve is controlled such that the interior of the fuel tank is under negative pressure during operation and stoppage of the engine.

Abstract: A residual fuel amount-estimating system for a fuel tank of an internal combustion engine installed in a vehicle. A pressure sensor detects the pressure within the fuel tank. The interior of the fuel tank is negatively pressurized, and a rate of change in the pressure within the fuel tank during negative pressurization is detected. A residual fuel amount within the fuel tank is estimated, based on the detected rate of change in the pressure within the fuel tank.

Abstract: A failure detection system detects a failure occurring in an exhaust secondary air supply system of an internal combustion engine, and has a catalytic converter installed in an exhaust pipe of an exhaust system of the engine for reducing pollutants from exhaust gases emitted from the engine, a conduit connected, at one end, to the exhaust pipe at a location upstream of the catalytic converter and an air pump connected to an opposite end of the conduit for supplying compressed air in the conduit. The conduit is closed by the a valve which opens in response to the negative pressure and a second valve which opens in response to the conduit pressure. In the system a first prescribed level and the second prescribed level are set and two pressure switches are provided for generating output at the levels. A failure occurring in the air pump and the valve is detected based on operation of the air pump and the output of the pressure detectors.

Abstract: An evaporative fuel-processing system for an internal combustion engine for a vehicle includes an evaporative fuel-guiding port for guiding evaporative fuel generated from the fuel tank, an adsorbent for adsorbing the evaporative fuel guided from the evaporative fuel-guiding port, an evaporative fuel-discharging port for discharging the evaporative fuel desorbed from the adsorbent, and an air-introducing port for introducing air. The system comprises a first passage for allowing the air-introducing port to communicate with the chassis side frame of the vehicle, and a second passage for allowing the air-introducing port to communicate with the engine room of the vehicle. A first one-way valve is arranged across the first passage, for allowing a flow from the chassis side frame of the vehicle to the air-introducing port, and a second one-way valve means is arranged across the second passage, for allowing a flow from the air-introducing port to the engine room of the vehicle.

Abstract: A catalyst deterioration-determining system determines deterioration of a catalyst arranged in the exhaust passage of an internal combustion engine. An ECU is responsive to an output from an O.sub.2 sensor arranged upstream of the catalyst or outputs from O.sub.2 sensors arranged upstream and downstream of the catalyst for controlling the air-fuel ratio of a mixture supplied to the engine by means of an air-fuel ratio correction value (first air-fuel ratio control). When the engine is in a predetermined operating condition, the system effects changeover from the first air-fuel ratio control to a second air-fuel ratio control which is responsive to the output from the downstream O.sub.2 sensor for controlling the air-fuel ratio of the mixture by means of the air-fuel ratio correction value.