A design is presented of an idle speed control system for a V-6 fuel injected engine. The controller synthesis is based on a frequency domain design methodology that parallels QFT (quantitative feedback analysis). In particular, the synthesis is aimed at maximizing the size of an external disturbance while preserving strict time domain constraints imposed on the system output, internal states and control efforts, with bandwidth limitations placed on the actuators. The engine model represents a V-6 fuel injected engine linearized about idle operating conditions at 800 rev/min, includes transportation lags and has its control efforts limited by the physical hardware. The design objective is to synthesize a controller(s) that maintains the idle speed within a prespecified percentage of the nominal in the presence of a torque disturbance representative of an automotive air conditioning compressor.