Abstract: In a V-type engine in which two air supply pipes are connected to banks thereof, respectively, two air-fuel ratio sensors are provided at positions downstream of the air supply pipes for producing outputs corresponding to the density of oxygen in exhaust emissions. When exhaust secondary air is supplied, differences between air-fuel ratio feedback correction factors calculated based on outputs of two air-fuel ratio sensors at a time and air-fuel feedback correction factors calculated at a time that is a time that results after a predetermined period of time has elapsed since the time are calculated. The differences so calculated are compared with a predetermined value, and, when the calculated differences do not exceed the predetermined value, the exhaust secondary air supply system is detected to fail.

Abstract: A controller provided in accordance with the invention determines a failure of a thermostat that opens and closes a passage through which cooling water circulates between a radiator and an engine. The controller prohibits the failure determination if a water temperature of the engine decreases by more than a predetermined amount during a predetermined period from the time when a rotational speed of the engine exceeds a predetermined rotational speed. Thus, when the thermostat opens due to a high rotational speed of the engine, the failure determination is prohibited. Therefore, it is avoided that the thermostat operating normally is judged to be faulty.

Abstract: A controller provided in accordance with the invention determines a failure of a thermostat that opens and closes a passage through which cooling water circulates between a radiator and an engine. The controller prohibits the failure determination if a water temperature of the engine decreases by more than a predetermined amount during a predetermined period from the time when a rotational speed of the engine exceeds a predetermined rotational speed. Thus, when the thermostat opens due to a high rotational speed of the engine, the failure determination is prohibited. Therefore, it is avoided that the thermostat operating normally is judged to be faulty.

Abstract: There is provided a valve timing control system for an internal combustion engine, which is capable of enhancing the accuracy of valve timing control. The valve timing control system 1 for the internal combustion engine 3 changes the cam phase of an intake cam 6a relative to a crankshaft 9, to thereby control the valve timing of an intake valve 4. The valve timing control system 1 fixes a desired cam phase CAINCMD at a value CAINCMDFC during an fuel cut-off, and controls a cam phase change mechanism 8 such that from a time t2 during the fuel cut-off, the cam phase is held at a value assumed at the time t2. Further, the valve timing control system 1 calculates a learned value DCALEARN of the amount of deviation of an actual cam phase CAIN based on a plurality of values of the actual cam phase CAIN detected at and after the time t2, and the constant value CAINCMDFC of the desired cam phase CAINCMD (step S5).

Abstract: There is provided a valve timing control system for an internal combustion engine, which is capable of properly setting the reference position of the cam phase by learning, and at the same time promptly establishing a learned value of the reference position when the learned value is lost, thereby accurately changing the cam phase for proper control of the valve timing of the engine. A cam phase change mechanism changes the cam phase. A reference value indicative of a reference position of the cam phase is learned at a predetermined learning speed based on the cam phase detected when the cam phase change mechanism is in a predetermined operative state, and the learned reference value (learned value) is stored in a RAM. When the loss of the learned value from the RAM is detected, a learning speed at the reference value is learned is corrected such that the learning speed is increased from the predetermined learning speed for a predetermined time period.

Abstract: There is provided a valve timing control system for an internal combustion engine, which is capable of properly setting the reference position of the cam phase by learning, and at the same time promptly establishing a learned value of the reference position when the learned value is lost, thereby accurately changing the cam phase for proper control of the valve timing of the engine. A cam phase change mechanism changes the cam phase. A reference value indicative of a reference position of the cam phase is learned at a predetermined learning speed based on the cam phase detected when the cam phase change mechanism is in a predetermined operative state, and the learned reference value (learned value) is stored in a RAM. When the loss of the learned value from the RAM is detected, a learning speed at the reference value is learned is corrected such that the learning speed is increased from the predetermined learning speed for a predetermined time period.

Abstract: There is provided a valve timing control system for an internal combustion engine, which is capable of enhancing the accuracy of valve timing control. The valve timing control system 1 for the internal combustion engine 3 changes the cam phase of an intake cam 6a relative to a crankshaft 9, to thereby control the valve timing of an intake valve 4. The valve timing control system 1 fixes a desired cam phase CAINCMD at a value CAINCMDFC during an fuel cut-off, and controls a cam phase change mechanism 8 such that from a time t2 during the fuel cut-off, the cam phase is held at a value assumed at the time t2. Further, the valve timing control system 1 calculates a learned value DCALEARN of the amount of deviation of an actual cam phase CAIN based on a plurality of values of the actual cam phase CAIN detected at and after the time t2, and the constant value CAINCMDFC of the desired cam phase CAINCMD (step S5).

Abstract: An evaporative emission control system for an internal combustion engine detects abnormality of the system based on pressure within a purging passage at a location between a purge control valve arranged therein and an intake passage of the engine, and pressure within a canister for adsorbing evaporative fuel generated from a fuel tank of the engine, when it delivers a valve opening command to open the purge control valve.

Abstract: A fuel supply control system for an internal combustion engine having an intake pipe, and a throttle valve arranged in the intake pipe. A basic value of a fuel amount to be supplied to the engine is determined based on a load on the engine. The determined basic value of the fuel amount is corrected by a correction value for increasing the fuel amount during and/or after acceleration of the engine. The correction value is determined based on a change in the opening degree of the throttle valve. The correction valve is further determined based on a change in the magnitude of the load on the engine.