Method of controlling internal combustion engine

1. A method for controlling an internal combustion engine comprising:

a coolant water temperature detecting means for detecting the coolant water temperature of the internal combustion engine,

a rotation speed detecting means detecting the rotation speed of the internal combustion engine, and

a control means controlling an operation of the internal combustion engine in accordance with the coolant water temperature and the rotation speed,

wherein a traveling with reduced cylinders, which reduces the number of engine cylinders injecting fuel for a certain period of time, is performed when the control means evaluates that the internal combustion engine is in a cold start state and that the rotation speed has reached a predetermined rotation speed after the engine starting,

wherein injection maps for the traveling with reduced cylinders, which are different from a normal traveling map, are memorized in the control means and the injection maps are referenced by the control means during the traveling with reduced cylinders,

wherein the traveling with reduced cylinders is performed until the coolant water temperature reaches a temperature preliminarily set up in a traveling with reduced cylinders downstream temperature map, which sets up the traveling with reduced cylinders downstream temperature corresponding to the coolant water temperature of the internal combustion engine at the starting,

wherein the traveling with reduced cylinders mode comprises at least two-stage or more multistage fuel injections into the operating cylinders, and

wherein the traveling with reduced cylinders mode of the internal combustion engine delays the main fuel injection starting timing relative to the timing in a normal traveling mode.

2. The method for controlling the internal combustion engine as set forth in claim 1 , wherein when the internal combustion engine is shifted to the condition equivalent to load traveling, the traveling with reduced cylinders mode promptly returns to the normal control mode.

3. The method for controlling the internal combustion engine as set forth in claim 1 , wherein the traveling with reduced cylinders mode of the internal combustion engine swiftly returns to the normal control mode when the internal combustion engine works at or above a prescribed rotation speed.

4. The method for controlling the internal combustion engine as set forth in claim 1 , wherein:

a misfire detecting means detects a misfire of the internal combustion engine in a combustion chamber, and

when the control means has evaluated that the misfire remains generated at the termination of the traveling with reduced cylinders, the traveling with reduced cylinders is continued for a certain period of time.

5. The method for controlling the internal combustion engine as set forth in claim 1 , wherein:

an intake air heating system which heats an intake air introduced into the combustion chamber of the internal combustion engine is provided, and

the intake air heating system works on the operating cylinders during the traveling with reduced cylinders.

6. The method for controlling the internal combustion engine as set forth in claim 1 , wherein:

a throttle mechanism, consisting of an intake throttle valve for controlling the intake volume to the internal combustion engine or an exhaust throttle valve for controlling the exhaust volume is provided, and

the throttle mechanism is not operated during the traveling with reduced cylinders and is operated after the traveling with reduced cylinders.