Ignition timing control system for an automotive engine

Claim 1

In an ignition timing control system for an automotive engine with an exhaust gas recirculation system having an exhaust gas recirculation passage and an exhaust gas recirculation valve operated by a vacuum operated actuator provided in the recirculation passage, the improvement comprising: a primary vacuum-advance means responsive to the vacuum at a first vacuum port located at a position just above a closed throttle position of an intake passage of the engine for advancing the ignition timing of the engine; secondary vacuum-advance means responsive to the vacuum at a manifold vacuum port of the intake passage for advancing the ignition timing in addition to the operation of the primary vacuum-advance mechanism; a first solenoid valve provided in a passage communicating secondary vacuum-advance mechanism with the manifold vacuum port; a second solenoid valve provided in a passage communicating a second vacuum port of the intake passage with a vacuum chamber of the vacuum operated actuator for the exhaust gas recirculation valve; an electronic control unit responsive to engine operating conditions in a low engine speed range except idling operation for closing the first and second solenoid valves to cut off the exhaust gas recirculation system and to cut off the passage for the first solenoid valve, thereby stopping the advancing of the ignition timing.