In a control system for a compression-ignition engine whose operation is
switchable between a compression-ignition operation in which an air-fuel
mixture supplied to a combustion chamber auto-ignites to burn owing to
compression and a spark-ignition operation in which the air-fuel mixture
is ignited to burn by a spark of a spark plug, it is determined whether a
predetermined prohibitive condition to prohibit switching from the
spark-ignition to the compression-ignition operation is satisfied, and
switching from the spark-ignition operation to the compression-ignition
operation is prohibited when the predetermined prohibitive condition is
satisfied, thereby enabling to avoid premature ignition and misfire and
to prevent drivability and fuel consumption performance from being
affected therefrom.