Air-fuel ratio control system for automotive engine

An air-fuel ratio control system for an automotive engine, having an engine speed sensor for detecting an engine speed, an air-fuel ratio sensor for detecting the condition of an air-fuel ratio of the engine, a fuel injection system with an injector for injecting fuel into a combustion chamber of said engine, and an intake air quantity measuring system including an intake air quantity sensor for detecting an intake air quantity;

• the control system comprising
• designation means for designating a learning region corresponding to an engine operating condition by selecting one of a first learning region for the measuring system and a second learning region for the injection system;
• first learning means responsive to a selection of said first learning region by said designation means for learning a first correction quantity in said measuring system from a discrepancy amount between a reference air-fuel ratio and an actual air-fuel ratio calculated in dependency on a signal output from said air-fuel ratio sensor;
• second learning means responsive to a selection of said second learning region by said designation means for learning a second correction quantity in said injection system from said discrepancy amount;
• and
• fuel injection quantity setting means for calculating a basic fuel injection quantity in dependency on said engine speed and for setting an actual fuel injection quantity with said first correction quantity learned by said first learning means and said second correction quantity learned by said second learning means.