Method for controlling the air-fuel mixture in an internal combustion engine

A method for controlling the titre of the air-fuel mixture in an internal combustion engine (2) provided with at least two cylinders (3), in which the exhaust gas present in a common exhaust manifold (6) is analysed in order to measure at least two successive values of the overall air-fuel ratio (AFRCOMP) of the cylinders (3); a value (AFRCIL; lambda CIL; DELTA CIL) of the air-fuel ratio of a final combusted cylinder (3) being estimated by carrying out a linear composition of the two successive values (AFRCOMP) of the overall air-fuel ratio of the cylinders (3) and the value (AFRCIL; XCIL; DELTA CIL) of the air-fuel ratio of the final combusted cylinder (3) being attributed to a first of the cylinders (3) and being used to correct a titre of the air-fuel mixture introduced into the first cylinder (3).