Abstract: A method of controlling the air fuel ratio in internal combustion, engines, comprising the steps of: updating first learning terms at a first learning speed in response to a signal from the air-fuel-ratio sensor and respectively storing them in a reloadable memory device, the first learning terms being provided for respective different ranges corresponding to different engine temperature and related to factors causing variation in air-fuel ratio in such a manner that the air-fuel-ratio variate of the variation varies depending upon the engine temperature; updating second learning terms at a second learning speed which is higher than the first learning speed in response to a signal from the air-fuel-ratio sensor and storing them in the reloadable memory device, the second learning terms being related to factors causing variation in air-fuel ratio in such a manner that the air-fuel-ratio variate of the variation varies in a substantially uniform manner with respect to the engine temperature; and determining the

Abstract: In an abnormality detection apparatus for vehicle engines, a deceleration discriminating circuit discriminates a deceleration state of a vehicle engine on the basis of a running state of the engine detected by a running state detector for detecting a running state of the vehicle engine. When the deceleration discriminating circuit determines that the engine is being in deceleration state, a comparing circuit compares a vehicle speed detected by a vehicle speed detector with a predetermined value. An abnormality deciding circuit is responsive to a comparison result signal from the comparing circuit to decide abnormality of the vehicle speed detector.