An engine control device is provided for reducing the retrieving time of control data from sensors at high and low engine speeds. Control parameters from the sensors are converted into memory access parameters to a control map to recover the desired injection amount. The fuel injection quantity is calculated by retrieving fuel injection amounts using the memory access parameters as addresses and performing a four-point interpolation of the memory parameters. A previously retrieved value is used as a reference value to aid the determination of an updated memory access parameter so that the retrieving time can be reduced for high and low engine speeds.