ENGINE CONTROL DEVICE

PROBLEM TO BE SOLVED: To maintain a constant stability in operating condition of an engine even when its idle speed is set at a lower level, with the use of an engine control system that comprises an ISC bypass passage bypassing the throttle valve, an ISC valve constricting the passage cross-sectional area and an alternator driven by the crankshaft and that serves to stabilize the idle operation by controlling the power generation of the alternator so that the battery voltage becomes a prescribed value and by increasing or decreasing the opening angle of the ISC valve in dependence on the variation in drive load of the alternator. SOLUTION: An engine control device A comprises an operating condition determination means 30b for determining an engine stall generation condition wherein the conditions liable to cause an engine stall are fulfilled when the engine speed Ne falls down to a preset speed Ne1, a load reduction means 30c for forcing down the target power generation value Ia of an alternator 31 upon such a determination, and an intake quantity reduction control means 30d for suppressing any reduction in bypass intake quantity gtotgal caused when the load reduction means 30c forces down the target power generation value Ia of the alternator 31.