A system for controlling fuel injection in an internal combustion engine such that when the target air-fuel ratio is switched from a rich value to a lean value, the air-fuel ratios are switched to the lean value by sequentially decreasing the amount of fuel injected into the cylinders, for...http://www.google.co.uk/patents/US5803048?utm_source=gb-gplus-sharePatent US5803048 - System and method for controlling air-fuel ratio in internal combustion engine 
