An engine control device includes an electronic control unit. The electronic control unit is configured to perform a spark discharge with an ignition plug for each cylinder by cutting off energization after elapse of a predetermined period from start of energization to an ignition coil for each cylinder of the engine, to stop the spark discharge caused by the ignition plug for each cylinder after supply of fuel to the engine is stopped when operation of the engine is stopped, and to control an ignition plug so as to stop the spark discharge caused by the ignition plug from a cylinder after a rotation speed of a crankshaft decreases gradually and the rotation speed of the crankshaft reaches a preset threshold value or less, after the stop of the supply of fuel to the engine.

A control method for an internal combustion engine in which a driving force is transmitted through a clutch to a driving wheel of a vehicle, the control method includes: when the internal combustion engine which is automatically stopped in a state where the clutch is disengaged is restarted, performing a torque down control to decrease a target torque of the internal combustion engine when the clutch is engaged; and setting a target torque in the torque down control, to a predetermined torque lower limit value determined in accordance with a driving state, the torque lower limit value including at least one of a predetermined full open value set when an accelerator opening degree is full open, and a predetermined full close value set when the accelerator opening degree is full close.

A control device for an internal combustion engine is configured to: execute a first decompression operating processing such that a decompression operating state is selected in a first engine speed region that passes in the course of engine stop; execute a decompression stop processing such that a switching from the decompression operating state to a decompression stop state is performed in the course of the engine stop after passage of the first engine speed region; when a temperature correlation value is greater than or equal to a threshold value upon an engine start-up request, execute a second decompression operating processing such that the decompression operating state is selected in a second engine speed region that passes in the course of engine start-up before the start of fuel injection. When the temperature correlation value is smaller than the threshold value, the second decompression operating processing is not executed.

Methods and systems are provided for dealing with a change of mind event during an automatic shut-down of an engine in which the speed at which a starter motor used to restart the engine is disengaged is based upon the comparison of current engine speed (N) with a cranking speed limit (S.sub.LIM). In one example, during an engine restart while the engine is spinning down, the starter motor may crank the engine to a threshold cranking engine speed adjusted based on a position of the gear.

Methods and systems are provided for diagnosing a vehicle fuel system and evaporative emissions system, and for diagnosing components in the evaporative emissions system. In one example, a method comprises activating an electric compressor while an engine that propels a vehicle is not in operation, to evacuate the fuel system and evaporative emissions system, sealing the fuel system and evaporative emissions system responsive to a threshold vacuum being reached during the evacuating, and indicating a presence or absence of non-gross undesired evaporative emissions based on a pressure rise in the sealed fuel system and evaporative emissions system. In this way, sources of undesired evaporative emissions may be readily detected, such that release of undesired evaporative emissions to the environment may be reduced.

Systems and methods for determining an idle, recommended cool-down period (RCDP) for a prime mover of a grounds maintenance vehicle. Delaying engine shutdown until after expiration of the RCDP allows engine components to adequately cool. In some embodiments, systems and methods may provide a quantitative indication of the time remaining in the RCDP, while other embodiments may notify an operator that a re-start of the engine is necessary to continue cool-down.

A vehicle control device configured to be capable of executing idle stop control to automatically stop an engine when a predetermined automatic stop condition is satisfied and restart the engine when a predetermined restart condition is satisfied during the automatic stop of the engine, the vehicle control device includes: a start request detector, a shift position detector, and a delay time setting module. A start request detector detects a driver operation indicating a request for starting the engine by a driver. A shift position detector detects a shift position of a shift changer. A delay time setting module sets, on a basis of presence or absence of the driver operation and the shift position, a delay time from when the engine is restarted until when an automatic stop of the engine is permitted.

Methods and systems are provided for diagnosing a cylinder valve deactivation mechanism in an engine system having cam-actuated valves. Movement of a latch pin of the deactivation mechanism is inferred from an induction current generated by a solenoid coupled to the latch pin, and the inferred movement is used to diagnose operation of cylinder valve deactivation mechanism. The inferred movement and a profile of the induction current is also used to estimate camshaft and crankshaft timing for improved cylinder fuel delivery in the absence of a camshaft sensor.

There are provided an intake pressure detecting means for detecting an intake pressure on more downstream side than a throttle valve in an intake passage to an engine, a rotational speed detecting means for detecting a rotational speed of an engine, an engine controlling means for controlling the engine to arrive at a target air-fuel ratio corresponding to the detected intake pressure and the detected engine rotational speed and an abnormality treating means for executing an engine stopping treatment to stop the engine if an intake pressure higher than a set pressure has been detected and an engine rotational speed higher than a set rotational speed has been detected, when an opening degree state detecting means detects that the throttle valve is under a fully closed or substantially fully closed state.

Disclosed is a method of alerting to the state of a high-pressure pump of an engine including a relief valve, a threshold pressure defining the opening pressure of the relief valve, the pump supplying fuel under pressure to a chamber equipped with a pressure sensor, including the following steps: initializing a computer when the engine is cut off during which cut-off a threshold pressure and a value of a first counter are collected in a memory associated with the computer; measuring the pressure of the fuel in the chamber; incrementing the first counter if the pressure of the fuel in the chamber is above or equal to the threshold pressure; and triggering an alert when the value of the first counter crosses a predetermined threshold.