A method of controlling the mass of air and fuel delivered to an internal combustion engine per cylinder per cycle by first determining the required fuel per cycle for the existing engine operating conditions, and then setting the air supply to the engine to provide the required air/fuel ratio for the determined fuel per cycle requirement. Thereafter, determining the actual air supply to the engine, and adjusting the fuel per cycle so the actual air/fuel ratio is greater or less than predetermined limits of the required air/fuel ratio. A look-up map can be provided in an electronic engine management system with preset air/fuel ratios against engine speed and load. The map is arranged with the predetermined limits of the required air/fuel ratio selected to prevent a specific condition such as engine misfire or for catalyst and/or emission considerations.
