Methods and systems are provided for diagnosing a positive crankcase valve during a vehicle key-off event. In one example, a method may include controlling a fluid flow from a crankcase of an engine to an intake manifold of the engine via a positive crankcase ventilation valve, and indicating whether the positive crankcase valve is stuck open responsive to spinning the engine unfueled in a reverse direction, and indicating whether the positive crankcase valve is stuck closed responsive to spinning the engine fueled but without spark in a forward direction. In this way, functionality of a positive crankcase ventilation valve may be diagnosed effectively during key-off conditions, which may prevent or reduce engine complications arising from a stuck open or stuck closed positive crankcase valve.

Methods and systems are provided for diagnosing a positive crankcase valve during a vehicle key-off event. In one example, a method may include controlling a fluid flow from a crankcase of an engine to an intake manifold of the engine via a positive crankcase ventilation valve, and indicating whether the positive crankcase valve is stuck open responsive to spinning the engine unfueled in a reverse direction, and indicating whether the positive crankcase valve is stuck closed responsive to spinning the engine fueled but without spark in a forward direction. In this way, functionality of a positive crankcase ventilation valve may be diagnosed effectively during key-off conditions, which may prevent or reduce engine complications arising from a stuck open or stuck closed positive crankcase valve.

A control apparatus for a hybrid vehicle is provided with: an air-fuel ratio determinator configured to determine an air-fuel ratio of an internal combustion engine in a predetermined period until speed change by a transmission is actually performed; and a controller configured to control at least one of the internal combustion engine and an electric motor in such a manner that a possible amount of torque down of the internal combustion engine is increased if the air-fuel ratio of the internal combustion engine is lean in the predetermined period. By this, it is possible to avoid a detrimental effect, such as a torque shock, deterioration of durability of a friction material, and the like, which can occur in the speed change.

A propulsion system, control system, and method are provided for optimizing fuel economy, which use model predictive control systems to generate first and second predicted actual axle torques and first and second predicted actual fuel consumption rates based on first and second sets of possible command values, respectively. The sets of possible command values include commanded engine output torques and commanded transmission ratios. First and second costs are determined for the first and second sets of possible command values, respectively, based on a first predetermined weighting value, a second predetermined weighting value, the first and second predicted actual axle torques, respectively, the first and second predicted actual fuel consumption rates, respectively, an axle torque requested, an engine output torque requested, a transmission ratio requested, and a fuel consumption rate requested. One of the first and second sets of possible command values is selected and set based on the lower cost.

A propulsion system, control system, and method are provided for optimizing fuel economy, which use model predictive control systems to generate first and second predicted actual axle torques and first and second predicted actual fuel consumption rates based on first and second sets of possible command values, respectively. The sets of possible command values include commanded engine output torques and commanded transmission ratios. First and second costs are determined for the first and second sets of possible command values, respectively, based on a first predetermined weighting value, a second predetermined weighting value, the first and second predicted actual axle torques, respectively, the first and second predicted actual fuel consumption rates, respectively, an axle torque requested, an engine output torque requested, a transmission ratio requested, and a fuel consumption rate requested. One of the first and second sets of possible command values is selected and set based on the lower cost.

The vehicle behavior control device comprises an engine control part operable, when an steering speed is greater than a predetermined threshold, and both of a steering wheel angle of a vehicle and the steering speed are increasing, to reduce an output torque of a multi-cylinder internal combustion engine along with an increase in the steering speed, and when the steering speed is equal to or less than the threshold, to stop the reduction of the output torque, and a threshold setting part operable, when the operation mode of the engine is the all-cylinder operation, to set the threshold to a first threshold T.sub.S1, and, when the operation mode of the engine is the reduced-cylinder operation, to set the threshold to a second threshold T.sub.S2 which is less than the first threshold T.sub.S1.

A hybrid vehicle includes: an engine, a motor configured to drive the vehicle, an air-fuel ratio sensor, and a control unit configured to stop and start the engine according to vehicle required power. The control unit is configured to change a threshold value of the vehicle required power at which the engine is started such that a difference between an air-fuel ratio detected by the air-fuel ratio sensor and a stoichiometric air-fuel ratio decreases in a case where the difference exceeds a predetermined value when the engine is stopped.

A vehicle control system is provided to promptly execute an ignition retard of the engine during shifting a gear stage in such a manner as to prevent an engine misfire, while switching air/fuel ratio from lean-burn ratio to stoichiometric ratio. An air/fuel ratio is switched between a stoichiometric ratio and a lean-burn ratio based on an operating point of an engine determined based on an engine speed and an engine torque. If a shifting operation of gear stage and a switching operation of the air/fuel ratio from the lean-burn ratio to the stoichiometric ratio are expected to be executed simultaneously, a controller delays the shifting operation of gear stage until completion of the switching operation of the air/fuel ratio.

An engine management apparatus for a vehicle. The apparatus comprises a fuel ratio controller arranged to control the air to fuel ratio of a fuel mixture for the vehicle's engine; a power demand sensor arranged to sense power demands made of the engine; and an engine controller configured to increase the air to fuel ratio from a first selected value to a second selected value in the event that the rate of vehicle speed change is less than a first threshold and the demand is less than a second threshold.

When a start request for an internal combustion engine is made with 1) a clutch disconnected, 2) a crankshaft rotating at a specified rotation speed or greater, and 3) fuel injection by an injector stopped, a controller for a vehicle executes: a first process that identifies, from the cylinders, a target cylinder that is in a compression stroke when the request is made; a second process that calculates a requested injection position based on the rotation speed; a third process that calculates, as a start crank position, a rotation position of the crankshaft advanced from the requested injection position by a specified rotation amount; and a fourth process that outputs a command signal that instructs a target injector to inject fuel at the crank position only if the rotation position of the crankshaft obtained when the request is made is advanced from the crank position.