Ignition timing compensation

Ignition timing compensation

Coolant Temperature Sensor

The coolant temperature sensor is a temperature dependent resistor (thermistor), the resistance of the thermistor decreases as the coolant temperature increases. When the ECM receives a low engine temperature signal from the coolant sensor on the K/G wire, it advances or retards the ignition timing to provide optimum driveability and emissions. The coolant temperature sensor earth is on the K/B wire.

Idle Speed Control

When the engine is at idle the ECM uses the fast response of ignition timing to assist idle speed control.

When loads are placed on, or removed from the engine the ECM senses the change in engine speed and in conjunction with the opening of the throttle disc by the stepper motor, advances or retards the ignition timing to maintain the specified idle speed.

NOTE: Due to the sensitivity of this system the ignition timing at idle is continually changing.