Abstract: In an engine management system which stores a control value FBPOS and increments or decrements this according to whether an oxygen sensor in the exhaust stream indicates that the engine is running lean or rich and which controls the duration of pulses applied to fuel injectors of the engine according to the deviation of the actual control value FBPOS from a reference value, a compensating adjustment is determined and applied to the pulse length duration in order to reduce any difference in the level of the actual control value FBPOS as between the closed-throttle running condition and either the open-throttle running condition or the reference value. The system thus serves to reduce the time taken to readjust upon opening and closing of the throttle and to minimize the emission of pollutants from the engine exhaust.

Abstract: An oxygen sensor which exhibits a change in electrical resistance as a function of oxygen partial pressure, comprises at least one of strontium ferrate (SrFeO.sub.3-x), barium ferrate (BaFeO.sub.3-x), and strontium barium ferrate (Sr.sub.1-b Ba.sub.b FeO.sub.3-x), where x is a variable and determines the degree of oxygen deficiency of the oxide, and b is 0 to 1, in which part of the iron in the ferrate lattice has been replaced by at least one element selected from the group consisting of zirconium, hafnium and tin.