| 摘要 |
An apparatus for use in an internal combustion engine operable on either of gasoline fuel and gasoline-alcohol fuel blend. The apparatus includes an alcohol concentration sensor for sensing the alcohol concentration of the fuel to be delivered to the engine, and an oxygen sensor sensitive to the oxygen content in exhaust gases discharged from the engine for producing an air/fuel ratio feedback signal. A difference of the air/fuel ratio from the stoichiometric value is calculated based on the air/fuel ratio feedback signal for a closed loop air/fuel ratio control. A correction factor is used to correct the amount of fuel delivered to the engine so as to provide fuel enrichment during high engine load conditions. In the event of failure of the alcohol concentration sensor, the amount of fuel delivered to the engine is determined with the alcohol concentration being set at a predetermined value. When the engine is operating with an effective closed loop air/fuel ratio control after the alcohol concentration is set at the predetermined value, both of the correction factor and the ignition timing are determined based on the calculated air/fuel ratio difference. If the closed loop air/fuel ratio control is clamped after the alcohol concentration is set at the predetermined value, the ignition timing is determined on an assumption that gasoline fuel is delivered to the engine, whereas the correction factor is set to inhibit the fuel enrichment.
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