APPARATUS FOR DETERMINING IMBALANCE OF INTER-CYLINDER AIR-FUEL RATIO OF INTERNAL COMBUSTION ENGINE

摘要

An apparatus for determining imbalance of inter-cylinder air-fuel ratio (determination apparatus) determines a value corresponding to the derivative value d(abyfs)/dt of detected air-fuel ratio abyfs represented by the output value Vabyfs from an air-fuel ratio sensor (67) when EGR gas is supplied as "a parameter Pon for determining imbalance during EGR supply", and determines a value corresponding to the derivative value d(abyfs)/dt when EGR gas supply is stopped as "a parameter Poff for determining imbalance during EGR stop ". The determination apparatus determines a value obtained by subtracting the parameter Poff for determining imbalance during EGR stop from the parameter Pon for determining imbalance during EGR supply as "a parameter Pegr for determining imbalance caused by EGR", and determines that imbalance state of inter-cylinder air-fuel ratio caused by EGR gas supply has occurred if the parameter Pegr is larger than a threshold Pegrth.