Abstract: A throttle opening range is divided into regions corresponding to the opening positions, and a deviation between an actual intake air suction state and a predetermined suction state provided for each of the divided regions is calculated. Intake system abnormality such as air cleaner clogging or intake pipe leakage is determined, if the deviation changes in a predetermined increasing or decreasing direction over a plurality of the divided regions. The air suction state may be represented by an intake pipe pressure or intake air flow quantity.

Abstract: A throttle opening range is divided into regions corresponding to the opening positions, and a deviation between an actual intake air suction state and a predetermined suction state provided for each of the divided regions is calculated. Intake system abnormality such as air cleaner clogging or intake pipe leakage is determined, if the deviation changes in a predetermined increasing or decreasing direction over a plurality of the divided regions. The air suction state may be represented by an intake pipe pressure or intake air flow quantity.

Abstract: A leakage diagnosing apparatus for an evaporated gas purge system, which executes purge system leakage diagnosis based on a detected pressure change amount and an introduced pressure which is introduced into a part of the purge system including at least a fuel tank and a canister. The detected pressure change amount is obtained by detecting pressure in the part of the purge system after such part of the purge system is hermetically sealed. Accordingly, the reliability of the leakage diagnosis is improved because an erroneous diagnosis caused by the introduced pressure is prevented. The detected pressure change amount may be compensated based on the introduced pressure into the sealed gas purge system. Accordingly, an erroneous leakage determination is prevented, and the reliability of leakage determination is improved.

Abstract: An ECU calculates an actual relative rotational angle in a VVT based on a crank angle signal sent from a crank position sensor and a cam angle signal sent from a cam position sensor. Furthermore, the ECU calculates a fundamental target relative rotational angle based on engine operating conditions. The fundamental target relative rotational angle is corrected by a factor responsive to the change of the air-fuel ratio. Thus, a control rotational angle fed to the VVT varies in accordance with the change of the air-fuel ratio so as to stabilize the combustion and improve the power output characteristics.

Abstract: A system that performs a highly precise air-fuel ratio control by considering the effect of purge. During an air-fuel ratio feedback operation, an amount of purge control AFPRG is calculated according to the following equation by the use of an actual TAU (actual amount of fuel injection) (step 602).AFPRG=actual TAU/(TP.times.FTHA.times.FPA)-(FTC+FPRG+FLAF)where TP represents a basic amount of injection, FTHA represents a suction air temperature correction factor, FPA represents an atmospheric pressure correction factor, FTC represents an acceleration/deceleration correction factor, FPRG represents a purge correction factor, and FLAF represents an air-fuel ratio learning correction factor.

Abstract: A valve timing control apparatus for an internal combustion engine includes a variable valve timing control mechanism of a hydraulic type which is provided in a drive force transmission arrangement for transmitting a drive force from a driving shaft to a driven shaft for actuating one of an engine-cylinder inlet valve and an engine-cylinder outlet valve, and which can relatively rotate one of the driving shaft and the driven shaft in a predetermined angular range. A detecting device operates for detecting a condition in which air enters hydraulic working fluid in the variable valve timing control mechanism. A trouble diagnosis device operates for implementing a trouble diagnosis on the variable valve timing control mechanism. An inhibiting device operates for inhibiting the trouble diagnosis implemented by the trouble diagnosis device when the detecting device detects the condition in which air enters hydraulic working fluid in the variable valve timing control mechanism.

Abstract: When a diagnosis execution condition is established, a canister closure valve is closed, thereafter, a purge control valve is opened, a purge control valve is closed in a state where negative pressure is introduced into an evaporated gas system to thereby maintain the evaporated gas system in a hermetically-sealed state and the hermetically-sealed state is continued until abnormality diagnosis is finished. Time period for maintaining the evaporated gas system in the hermetically-sealed state is divided into three time periods of a pressure change determining time period at a first time, an awaiting time period and a pressure change determining time period at a second time.

Abstract: A system and method for determining abnormality of a VVT (variable valve-timing control mechanism) and controlling the VVT on consideration of responsiveness thereof. When execution conditions for abnormality determination of the VVT are present, speed of change in angle of rotation ACSPD is calculated on a basis of transition in actual angle of rotation of the VVT as a responsiveness-detection parameter. In the abnormality determination, if the speed of change in angle of rotation ACSPD is less than a programmed determination value, it is determined that followup of VVT operation is faulty, and an abnormality-determination flag XVTFAIL is set to "1" to indicate that some abnormality has occurred. Also, a warning light is placed in an illuminated state. Target relative angle of rotation of the VVT is appropriately established, and VVT operation is suppressed on the basis of this abnormality determination. As a result, drivability and emissions performance degradation can be suppressed.

Abstract: A valve timing control apparatus for an internal combustion engine includes a variable valve timing control mechanism of a hydraulic type which is provided in a drive force transmission arrangement for transmitting a drive force from a driving shaft to a driven shaft for actuating one of an engine-cylinder inlet valve and an engine-cylinder outlet valve, and which can relatively rotate one of the driving shaft and the driven shaft in a predetermined angular range. A detecting device operates for detecting a condition in which air enters hydraulic working fluid in the variable valve timing control mechanism. A trouble diagnosis device operates for implementing a trouble diagnosis on the variable valve timing control mechanism. An inhibiting device operates for inhibiting the trouble diagnosis implemented by the trouble diagnosis device when the detecting device detects the condition in which air enters hydraulic working fluid in the variable valve timing control mechanism.

Abstract: An air/fuel ratio controller for an internal combustion engine that obtains stabilized air-fuel ratio controllability even when an air-fuel ratio is changed during purge execution. In purge control to discharge fuel vapor adsorbed in a canister to an intake-air side of an internal combustion engine, the controller controls a purge ratio, by controlling operation of the purge solenoid valve, even when an air-fuel ratio is changed. A fuel-injection quantity from an injector is then compensated in correspondence thereto. Thus, stabilized air-fuel ratio controllability can be obtained by correction with a fuel-injection quantity, or purge correction by a control duty of the purge solenoid valve as a purge control parameter, even when an air-fuel ratio .lambda. is changed during purge execution, taking a predetermined ratio as the purge ratio.

Abstract: A control method and system that achieves a desired purge flow rate in accordance with operation of a variable valve timing control mechanism. Although pumping loss of an internal combustion engine is varied by a change in the amount of operating the variable valve timing control mechanism, a change in an intake pressure in an intake passage is caused by influence of inertia supercharging, and the purge flow rate is changed. In this case, an opening degree of a purge solenoid valve is set according to the respective amount of operating the variable valve timing control mechanism. The set opening degree is considered by the ECU, and a final opening degree of the purge solenoid valve is set, so that a desired purge flow rate can be controlled regardless of the operation of the variable valve timing control mechanism.

Abstract: An evaporated fuel gas purging system performs breakdown analysis without deterioration of drivability and exhaust emission even when the amount of purged fuel gas is large. During introduction of negative pressure into the purge system, a control value DUTY sets opening of a purge control valve and a purge flow amount GPG is derived from a map based on differences in the control value DUTY, atmospheric pressure and intake pipe pressure. Thereafter, a purge ratio PGR is calculated from intake air GA and purge flow GPG (PGR=GPG/GA), and a fuel injection correction value FAFLEAK=PGR.times.(FGPGAV-1).times.K1 is calculated, with FGPGAV-1 being the air-fuel ratio feedback correction deviation per 1% purge ratio, and K1 being an error correction coefficient. Then, the fuel injection correction FAFLEAK is guard-processed to maintain it below an upper limit guard value KFLEAKMX.

Abstract: When refueling is started, a purge valve is closed, and power is supplied to a coil of a solenoid so that a constant pressure operating valve of an atmospheric escape valve is opened. When the temperature of the fuel tank rises while an engine is at a stop, fuel evaporation gas generates and the pressure within the fuel tank increases. When the differential pressure between the in-tank pressure and the atmospheric pressure increases, a first communication passage is opened, and the pressure is released to the outside. Thus, the pressure within the fuel tank can be maintained at an appropriately high pressure level while the vehicle is at a stop, and the quantity of the fuel evaporation gas generating while the vehicle is at a stop can be controlled.

Abstract: A canister for preventing diffusion of fuel vapor to atmosphere is disclosed herein. The canister includes a first case having an adsorbent material, such as activated charcoal, therein and a second case also having an adsorbent material therein. The two cases are joined by a passage having a valve disposed therein. The valve regulates the airflow between the two cases. The first case is connected to the valve, a gas tank, and an engine, while the second case is connected to the valve and to atmosphere. During a refueling operation, the valve is operated so as to allow air to flow from the tank, through the first case and out to the atmosphere through the valve, without passing through the second case.

Abstract: A canister is provided between a fuel tank and an intake conduit of an engine so that fuel vapor generated in the tank and adsorbed in the canister is purged into the intake conduit. In correcting a fuel quantity in accordance with a purge quantity, the fuel quantity is compensated for by a canister piping condition such as a pressure loss and/or a purge delay. A first fuel correction coefficient is calculated from canister pressure, intake pressure and atmospheric pressure. The first coefficient may be calculated in association with an idling speed control value. A second fuel correction coefficient is calculated from changes in purge flow quantity and canister pressure. The second coefficient may be calculated in association with an air-fuel ratio feedback control value.

Abstract: An air/fuel control system for an internal combustion engine or the like delivers evaporated gas from the engine's fuel tank and adsorbed in a canister to an intake of the engine via a discharge route. A purge vacuum switching valve (VSV 16) disposed in the discharge route controls the rate at which the evaporated gas is delivered to the engine intake. Using a sensor, the air/fuel ratio of the engine intake is determined and the deviation of the detected air/fuel ratio from a target ratio calculated according to learned air/fuel ratio parameters is calculated. The density of the evaporated fuel stream is determined based on that deviation, and the VSV is driven based on the calculated evaporated gas density. If the air/fuel parameters are not learned within a predetermined time, the VSV is driven at a fixed rate. A drive signal to the engine's fuel injection system also may be corrected based on the calculated evaporated fuel density.

Abstract: A system for solving disturbances in the air-fuel ratio caused by a change in the normal correction factor, and permitting achievement of a highly accurate air-fuel ratio control. Fuel evaporative gas generated in a fuel tank is adsorbed in a canister, and then discharged into an intake pipe of an internal combustion engine. ECU calculates the fuel supply quantity to the internal combustion engine on the basis of the condition in which the internal combustion engine is operating, performs feedback control and learning control of an air-fuel ratio on the basis of a detection signal from an oxygen sensor, and corrects the fuel supply quantity by means of an air-fuel correction factor. ECU also controls fuel injection by an injector by decrement-correcting the fuel supply quantity in response to the quantity of discharged evaporative gas.

Abstract: In a fuel vapor purge mechanism, the fuel vapor generated from a fuel tank and stored in a canister undergoes flow volume control with a purge solenoid valve while being introduced to an intake system of the engine via a purge passageway. Meanwhile, in an air/fuel ratio feedback control system, by means of a linear air/fuel ratio sensor mounted on an exhaust system of the engine, the air/fuel ratio of air-fuel mixture of fuel and intake air including the fuel vapor. If a change amount of a purge ratio the fuel vapor goes above a determined value, there is compensation of the air/fuel ratio compensation coefficient FAF concerned with the feedback control based on the change ratio.

Abstract: An air-fuel ratio control apparatus of an internal combustion engine capable of learning and controlling an air-fuel ratio accurately both in idling and non-idling without being affected by concentration of evaporated fuel. Uniform deviation of an air-fuel ratio is detected before starting purging of the evaporated fuel (steps S133 to S137), air-fuel ratio learning values KGI.sub.0 to KGI.sub.7 and KGS.sub.0 to KGS.sub.7 are stored respectively so that the uniform deviation shows a predetermined value or lower both at idling time and at non-idling time (steps S138 to S142), and air-fuel learning values KG.sub.0 to KG.sub.7 in respective areas including idling are updated or renewed with a value obtained by leveling or averaging air-fuel ratio learning values KGI.sub.0 to KGI.sub.7 and KGS.sub.0 to KGS.sub.7 stored both at idling time and at non-idling time (step S145).

Abstract: An air-fuel ratio controller of an internal combustion engine for preventing that an air-fuel ratio in the beginning of the purging operation of evaporated fuel is excessive. Evaporated fuel produced within a fuel tank is absorbed in a canister and the evaporated fuel absorbed in the canister is purged to the air intake side of the internal combustion engine through a purge valve together with air. A concentration of the evaporated fuel is detected by an air-fuel ratio feedback value detected by an oxygen sensor and a fuel injection quantity is corrected to be reduced in accordance with the detected evaporated fuel concentration and the purge ratio. When the air-fuel ratio feedback value exceeds a predetermined value or an output of the oxygen sensor is rich during the purging operation, it is judged that detection of concentration is insufficient and the update value for detection of concentration is made larger than a usual value.