Method and apparatus for controlling engine idling speed

In an apparatus for controlling the idling speed of an engine having speed sensor means for sensing a rotational speed of said engine, temperature sensor means for sensing a temperature of said engine, electronic control means responsive at least to output signals of said speed sensor means and said temperature sensor means to generate a control amount signal for controlling an idle air flow to said engine, and air control valve means responsive to said control amount signal from said control means so as to control said idle air flow, the improvement wherein said control means includes:

• digital input port means for receiving the output signal of said speed sensor means;
• analog input port means for receiving the output signal of said temperature sensor means;
• microprocessor means responsive to output information of said digital input port means and said analog input port means for computing a control amount which consists of a basic control amount and a correction value;
• memory means for storing said control amount computed by said microprocessor means and supplying desired information to said microprocessor, said basic control amount being preset into said memory means when, in accordance with the output signal of said temperature sensor means, it is determined that said engine is at a warm-up operation, and said correction value being stored in said memory means when the engine has warmed up completely, and rewritten in accordance with the difference value between a target value and the actual rotational speed of the engine;
• and
• means for converting a digital output of said microprocessor relating to said idle air flow to operate said air control valve means.