5224454 A abstract an air fuel ratio feedback control method for an internal combustion engine having an exhaust gas ingredient concentration sensor arranged in the exhaust passage and having output characteristics in approximate proportion to the concentration of an ingredient in exhaust gases from the engine wherein when the engine is in a predetermined operating condition the air fuel ratio of an air fuel mixture supplied to the engine is feedback controlled to a desired air fuel ratio dependent on the predetermined operating condition of the engine and when the engine is in a predetermined deceleration condition the fuel supply to the engine is cut off when the engine has shifted from an operating condition other than the predetermined deceleration condition to the predetermined deceleration condition the desired air fuel ratio is held at a value assumed immediately before the engine shifts from the operating condition other than the predetermined deceleration condition to the predetermined deceleration condition for a predetermined time period after the shifting the feedback control of the air fuel ratio is started with the held value as an initial value of the desired air fuel ratio when the engine has shifted to the predetermined operating condition preferably the desired air fuel ratio is held at a value substantially corresponding to a central value of air fuel ratio after the predetermined time period has elapsed application_number US 75147891 A description the method according to the invention will now be described in detail with reference to the drawings showing an embodiment thereof referring first to fig1 there is shown the whole arrangement of a fuel supply control system which is adapted.