Abstract: A fuel control system for an internal combustion engine, including a fuel flow control sensitive to one or more engine operating parameters and controlling the rate at which fuel is introduced into the engine, an exhaust gas sensing device for producing an output signal corresponding to the exhaust gas composition, feed back means for feeding back to the fuel flow control, a signal derived from said output signal to correct the fuel flow, said feed back means including a signal storage device, the signal stored in which is altered in accordance with variations in the output signal of the exhaust gas sensing device, and overrun detection means connected to said feed back means and arranged to prevent alteration of said stored signal by the exhaust gas sensing device during overrun.