Abstract: A failure-detecting device detects failure of a tank internal pressure sensor for an internal combustion engine. The tank internal pressure sensor is provided in a fuel tank for detecting pressure within the fuel tank. The failure of the tank internal pressure sensor is detected by detecting an amount of variation in an output from the tank internal pressure sensor occurring within a predetermined time period elapses after the start of the engine and determining that the tank internal pressure sensor is abnormal when the amount of variation is below a predetermined value upon the lapse of the predetermined time period. A fail-safe device inhibits abnormality diagnosis of the evaporative emission control system when it is determined that the tank internal pressure sensor is abnormal.

Abstract: A misfire-detecting system for an internal combustion engine in which a value of sparking voltage is detected, which is generated across a spare plug when high voltage is generated by an ignition device in response to generation of an ignition command signal. When a time period over which the detected value of sparking voltage exceeds a predetermined reference voltage value exceeds a predetermined time period value, the system determines that a misfire has occurred in the engine. A recharging command signal is generated for applying high voltage to the spark plug, after generation of the ignition command signal. As a result, a misfire can be accurately detected.

Abstract: Misfire detection system for an internal combustion engine. If misfire is found to occur due to vapor lock temporarily happening, it will erroneously be judged that the structure of the engine or the fuel supply system is out of order. However, vapor lock is an interruption of the flow of fuel in a gasoline engine caused by formation of vapor or gas bubbles, and does not mean the engine or the fuel supply system is degraded in its structure. On the contrary, if misfire is detected in such situation, the misfire detection degrades the reliability of the system. The misfire detection is therefore inactivated during conditions in which vapor lock is liable to occur, by discontinuing the detection, or by deliberately deeming no misfire to occurs even if it is so detected. Alternatively, the reference level for misfire detection is raised during such conditions.

Abstract: An evaporative fuel-processing system for an internal combustion engine, in which a first control valve is arranged across an evaporative fuel-guiding passage extending from a fuel tank to a canister, a second control valve across a purging passage extending from the canister to the intake system of the engine, and a third control valve at an air inlet port of the canister, respectively. An ECU generates operation command signals to the first to third control valves for closing or opening the same. The ECU is responsive to an output from a tank internal pressure sensor which detects pressure within the fuel tank and the operation command signals, for detecting an abnormality in operation of a predetermined one of the first to third control valves.

Abstract: An evaporative fuel-processing system for an internal combustion engine includes an evaporative emission control system having a canister, a first passage connecting between the canister and a fuel tank, a second passage connecting between the canister and the intake system of the engine, and a purge control valve arranged across the second passage, a drain shut valve for opening and closing an inlet port of the canister, and pressure sensors for detecting pressure within the evaporative emission control system. The evaporative emission control system is negatively pressurized by introducing negative pressure from the intake system into the evaporative emission control system by opening the purge control valve and closing the drain shut valve, to thereby bring the evaporative emission control system into a predetermined negatively pressurized state, and then closing the purge control valve to complete the negative pressurization.

Abstract: A fuel supply control system which controls an amount of fuel supplied to an internal combustion engine. An ECU detects a value related to an amount of combustion ions generated within cylinders. The detected value is compared with a predetermined value, and the amount of fuel supplied to the engine is corrected based upon the comparison result, when the engine is in a transient operating condition, such as acceleration and deceleration, whereby the responsiveness of the air-fuel ratio feedback control is enhanced to improve drivability and exhaust emission characteristics.

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.

Abstract: Disclosed is an evaporative fuel purging apparatus used for an internal combustion engine. A canister having an absorbing agent for absorbing an evaporative fuel generated in a fuel tank of the internal combustion engine is provided. A drain control valve is provided on a drain port for opening the canister to the atmospheric air, and which is adapted to open and close the drain port. A purge control valve is provided on a purge passage communicating the canister to a part of an intake system, and which is adapted to purge the evaporative fuel absorbed into the canister through opening and closing the purge passage. A diagnostic device diagnoses the presence or absence of leakage in a purge system which is sealed up by closing the drain control valve and the purge control valve after pressure-reduction treatment.

Abstract: An evaporative fuel processing system adapted to be capable of detecting abnormality of an evaporative emission control system for storing, in a canister, evaporative fuel generated from a fuel tank for holding fuel to be supplied to an internal combustion engine, and purging evaporative fuel into the intake system of the engine. A first control valve is arranged across a passage extending between the fuel tank and the canister. A second control valve is arranged across a passage extending between the canister and the intake system of the engine. A third control valve is provided for an air inlet port of the canister communicatable with the atmosphere. Through operating these control valves to open and close them, the evaporative emission control system is negatively pressurized, and abnormality of this system is detected based on the pressure detected in this negatively pressurized state thereof. Timing for carrying out abnormality determination is determined depending on conditions of the fuel tank.

Abstract: A failure-detecting device detects failure of a tank internal pressure sensor for an internal combustion engine. The tank internal pressure sensor is provided in a fuel tank for detecting pressure within the fuel tank. The failure of the tank internal pressure sensor is detected by detecting an amount of variation in an output from the tank internal pressure sensor occurring within a predetermined time period elapses after the start of the engine and determining that the tank internal pressure sensor is abnormal when the amount of variation is below a predetermined value upon the lapse of the predetermined time period. A fail-safe device inhibits abnormality diagnosis of the evaporative emission control system when it is determined that the tank internal pressure sensor is abnormal.

Abstract: A tank internal pressure-detecting device for an internal combustion engine having an evaporative emission control system for controlling purging of evaporative fuel generated in a fuel tank thereof into an intake system thereof. An ECU interrupts purging of evaporative fuel by the evaporative emission control system for a predetermined period of time after the engine is started. The ECU causes control valves of the evaporative emission control system to open the interior of the fuel tank to the atmosphere, and stores a value of pressure within the fuel tank detected by a tank internal pressure sensor as a reference value while the purging is being interrupted and at the same time the interior of the fuel tank is opened to the atmosphere. The ECU corrects an output value of the tank internal pressure sensor, based upon the reference value stored.

Abstract: An abnormality detection system is provided, which detects abnormality in an evaporative fuel control system for an internal combustion engine. A plurality of temperature sensors are arranged in an evaporative fuel storage device at different locations for detecting the temperature of an adsorbent or in the vicinity thereof within the storage device at the different locations. An ECU controls at least one of charging of evaporative fuel from the fuel tank to the storage device and purging of evaporative fuel from the storage device to the intake system of the engine. The ECU determines the presence or absence of an abnormality in the evaporative fuel control system, based upon output values from the temperature sensors assumed when the control system is operative. A state in which adsorption of evaporative fuel generated in the fuel tank to the adsorbent of the storage device has been completed is detected, based upon the amount of a rise in temperature detected while the charging is being effected.

Abstract: A misfire-detecting system detects a misfire occurring in an internal combustion engine. A value of sparking voltage for discharging a spark plug of the engine is detected. The detected value of the sparking voltage is compared with a first predetermined value. A degree to which the detected value of the sparking voltage exceeds the first predetermined value is measured. The measured degree is compared with a second predetermined value. It is determined based upon results of the latter comparison whether or not a misfire occurred in the engine. According to a first aspect of the invention, the second predetermined reference value is set based upon detected values of operating parameters of the engine. According to a second aspect of the invention, the determination of occurrence of a misfire is inhibited when the engine is in a predetermined operating condition.