Abstract: A method and system for controlling air/fuel ratio of an internal combustion engine during cold start operation utilizes control logic to determine a base fuel pulsewidth and a base spark timing according to corresponding cold-start look-up tables. A crank angle of the engine at which a peak pressure in the cylinder occurs is then sensed to obtain a crank angle at peak pressure (PPCA) value. Upon reaching stable combustion, the base fuel pulsewidth and the base spark timing are ramped to a predetermined desired fuel pulsewidth and a predetermined desired spark timing based on the PPCA value so as to control the air/fuel ratio. Upon reaching this state, combustion stability is maintained by feedback control of fuel pulsewidth and spark timing based on the statistical variation of successive PPCA values.