Engine control method for reducing emissions during cold start and idling for vehicle

DETAILED DESCRIPTION The present invention provides an engine control method for decreasing hydrocarbon emissions during cold start and engine idling by retarding the ignition timing and controlling the engine to idle under a lean air/fuel ratio, and controlling the amount of injected fuel according to a suitable quantity of wetting fuel.
In accordance with the present invention, the engine is cranked under a leaner air/fuel ratio than a stoichiometric air/fuel ratio by maximizing the amount of intake air in the early stage of the engine starting, and minimizing the engine load caused by an automatic transmission.
The quantity of wetting fuel is preferably calculated based on the number of power strokes of a specific cylinder and the total number of power strokes of the engine that have an effect on temperature of the specific cylinder.
After starting, for a certain time period, idle speed is regulated by ignition timing in a state such that a maximum amount of intake air is secured.
In one embodiment, the engine control method according to the present invention comprises opening the ISA to a predetermined open position such that an air/fuel ratio becomes higher (leaner) than a stoichiometric air/fuel ratio, and minimizing engine load from the automatic transmission.
The air/fuel ratio and ignition timing are controlled based on engine speed and engine load, and the amount of injected fuel is controlled based on the quantity of wetting fuel.
The air flow rate is determined according to engine speed and coolant temperature.
Air/fuel ratio and ignition timing are then controlled in order to control engine speed fluctuation based on engine speed and engine load.
According to a further preferred embodiment, the ISA is fully opened and the engine load due to the automatic transmission is minimized by controlling line pressure in the automatic transmission such that no line pressure is generated.
Then the air/fuel ratio is set at a value higher than a stoichiometric air/fuel ratio, ignition timing control is performed, and the amount of fuel injected is controlled based on the quantity of wetting fuel that is determined in consideration of the number of power strokes in a specific cylinder and the total number of power strokes of a specific engine