A control system for an internal combustion engine provides controlled engine spark timing which is a function of a plurality of individual timing signals. These individual signals include a throttle advance signal, a programmed vacuum advance signal, a break-idle advance signal, an engine start advance signal, an engine speed advance signal and a fixed timing signal. These signals are algebraically summed together to develop a resultant spark timing signal representing desired spark timing. Individual signals are derived from transducer circuits which are responsive to various engine operating and/or ambient conditions. The throttle advance signal is a function of both a throttle position signal and a throttle rate signal and provides increasing advance as the throttle increasingly opens. It is also attenuated as the temperature of ambient air entering the engine for combustion increases. The programmed vacuum advance signal programs the vacuum advance in accordance with an accumulation function which is representative of the duration for which the engine has been operating in selected operating modes, namely idle and non-idle. The break-idle advance signal provides momentary advance when the engine throttle is displaced from the idle position. The engine start advance signal provides advance for a short interval after the engine has been started. The engine speed advance signal provides increasing advance as the engine speed increases. The fixed timing signal provides fixed timing which is used to adjust the basic timing for a given set of engine operating conditions. The control system is particularly advantageous when used in an engine which uses a leaner fuel-air mixture (17-18:1, for example) in comparison to presently used mixtures (15-16:1). Improvement accrues by way of reduction in exhaust emission products and better fuel economy.