Electronic Spark Advance

ESA System Diagram:

This system controls electronically the time of electric current flow to ignition primary coil as well as ignition timing.

ECM judges the engine condition by using signals from various sensors, selects the most suitable electric current flow time and ignition timing for that engine condition from among those prestored in its memory and sends a signal to the power unit.

The power unit turns ON and OFF the primary current of the ignition coil according to the signal from ECM.

Control of this system includes four different types as follows.

- Ignition timing control at engine start
- Ignition timing control at engine idling
- Ignition timing control at any time other than engine start and idling
- Electric current flow time control

Ignition Timing Control At Engine Start
To obtain better starting performance of the engine at the engine start (when the engine start switch is turned ON or the engine speed is lower than 400 rpm.) ESA system sets the ignition timing to the initial ignition timing (6° BTDC).

Ignition Timing Control At Engine Idling
When the idle switch is ON and the car speed is lower than 20 km/h (12 mph), the final ignition timing is determined by adding a compensation which varies with the engine speed to the ignition timing determined according to the engine cooling water temperature.

Ignition Timing Control At Any Time Other Than Engine Start And Idling
Under any conditions other than the above (with the idle switch OFF and the engine running), the ignition timing is determined according to the intake air volume and the engine speed.

Electric Current Flow Time Control
To stabilize the secondary voltage generated in the ignition coil to a proper level, ESA system controls the time of primary current flow to the ignition coil.

NOTE: The ignition timing is controlled by ECM as described above. Therefore, when checking or adjusting the ignition timing, the ignition timing must be fixed to the initial one by grounding the test switch terminal.