Abstract: An Air/Fuel mixture control system for an internal combustion engine which uses a closed loop controller for varying an air/fuel mixture in response to the voltage output of the engine's exhaust gas oxygen sensor. The oxygen sensor will produce a voltage output which is classified in a range extending from very rich, net rich, net lean or very lean depending upon the sensed voltage output in milli-volts. The controller responds to an onset of a lean or rich exhaust signal, representative of either too much or too little oxygen, by instructing the fuel injectors to either increase or decrease the fuel delivery rate to a predetermined rich step value or lean step value. The delivery rate at the rich or lean step value is maintained until the onset of either a rich or lean exhaust indication or until a predetermined rich or lean step duration expires.

Abstract: A true closed-loop air/fuel ratio control system for an internal combustion engine which uses a cylinder air charge percentage value also known as a cylinder or engine load value, is used to control the air/fuel ratio of said engine in response to the difference of said measured load value and a predetermined optimum load value. This process allows true closed-loop fuel control immediately following a cold or warm engine start without need of a traditional exhaust gas sensor. As this process automatically compensates for all fuel utilized by the engine, even during cold starting and idles, the problems associated with fuel vapor purge systems are eliminated. This process can reduce government regulated emissions from said engine considerably and improve fuel economy a significant percentage particularly when operated net lean of stoichiometric. Elimination of currently required engine hardware for traditional systems can allow for a considerable cost savings.