The invention relates to an engine controller 100 comprising a combustion state detection or estimation means for detecting or estimating a combustion state in the combustion chamber 17, a combustion air-fuel ratio estimation means for estimating a combustion air-fuel ratio in the combustion chamber according to an exhaust air-fuel ratio and the detected or estimated combustion state, and a means for calculating engine control parameters according to the estimated combustion air-fuel ratio.
Whereby, an inexpensive engine controller can control the combustion air-fuel ratio at the time of start with high precision.