An electronic control system of the automobile engine for optimal start and idle speed control has been developed. This system employs the microcoputer-based electronic control unit and crank angle sensor for precise control on fuel injection, ignition timing, and idle speed more quickly and accurately at the start and idling. Consequently, the number of misfire can be reduced during been affected by air flow rate, idle quality(roughness), spark timing, fuel injection, water temperature, and load, Thus, this electronic control system strivers to reach the optimal idle operating point, defined the lowest idle speed(fuel economy) and idle quality(roughness), under any engine operating conditions.