AIR/FUEL RATIO CONTROL SYSTEM FOR INTERNAL COMBUSTION ENGINE WITH VARIABLE CONTROL CHARACTERISTICS DEPENDING UPON PRECISION LEVEL OF CONTROL PARAMETER DATA

An air/fuel ratio control system detects an air/fuel ratio indicative control parameter out of required precision range for initiating a control characteristics derivation process. The control characteristics derivation process is performed by varying constant consisting an air/fuel ratio dependent fuel delivery amount correction coefficient in trial basis to monitor fluctuation range of the correction coefficient. Based on the trial basis processings, the value of the constant is determined so as to compensate the precision level lowered in monitoring the air/fuel ratio.