Ignition timing compensation

Manifold absolute pressure (MAP) sensor The LOAD signal is detected by the MAP sensor located in the ECM which detects manifold pressure via a hose connected to the inlet manifold. This sensor converts pressure variation in the inlet manifold into graduated electrical signals which the ECM can use to determine the engine load.

Ignition timing compensation

Engine Coolant Temperature (ECT) Sensor The ECT 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 ECT sensor, it advances or retard the ignition timing to provide optimum driveability and emissions.

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 IACV, 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.

Knock (KS) sensor ( T Series only ) The KS sensor is a capacitive device mounted in the cylinder block between number 2 and 3 cylinders below the inlet manifold. The sensor monitors noise and vibration in the engine and passes this information to the ECM which is able to identify the characteristics of the knocking and make the necessary adjustments to the ignition timing of individual cylinders.