A method for controlling the air-fuel ratio in an internal combustion engine which includes the steps of changing the air-fuel ratio to a predetermined extent, detecting changes in the operating conditions of the engine by running the engine on the basis of the changed air-fuel ratio, and correcting...http://www.google.com.au/patents/US4538578?utm_source=gb-gplus-sharePatent US4538578 - Air-fuel ratio control for an internal combustion engine
