PURPOSE: To maintain a proper air fuel ratio by preventing an excessive fuel injection caused by over shoot of thermal air flow meter output just after turning on electric power supply and during a transient time.

CONSTITUTION: Just after a starter switch is turned on, and during idling condition till a prescribed time passes after the starter switch is changed from on- condition to off-condition, an allowable value (TPS) is set on the basis of a cooling water temperature (TW) (S208), and the allowable value (TPS) is set to a ceiling value (TPMAX) in relation to a basic fuel injection pulse width (TP) (S209). On the other hand, after a prescribed time passes after the starter switch is changed from ON-condition to OFF-condition or during non-idling condition, the ceiling value (TPMAX) in relation to the basic fuel injection pulse width is set to a constant value (TPK) (S210). By suppressing the basic fuel pulse width to the ceiling value (TPMAX) or less, over rich condition of an air fuel ratio caused by output over shooting of a thermal air flow meter at the time of starting is prevented so as to improve starting property, and also deterioration of the air fuel ratio caused by over shooting of output at a transient time of the thermal air flow meter is prevented.