When starting the engine, the ECM calculates the fuel needed by comparing value from the coolant and fuel temperature sensor, and the crankshaft and throttle position sensors, It calculates idle speed according to coolant temperature and engine load for example: electrical kit can alter idle load significantly. During idling, when firing irregularities are more noticeable, injection quantity is corrected continually to give stable revs. Sudden unintended movement in the accelerator pedal and vibrations in other components caused by, say, road defects could cause an intolerable jerking in the fuelling and engine firing. To counter this, the ECM compares the engine speed signal with the rate of throttle movement, and signals corrections to the quantity control servo to ensure smooth running.
The ECM limits the maximum revs by controlling the injection quantity. The fuel quantity injected at fuel engine load is varied by the ECM according to air temperature, altitude and coolant temperature. At high air temperatures and high altitude maximum quantity is reduced to keep emissions acceptable. The full load fuel quantity is also reduced if high coolant temperature is detected. The ECM will also cut the aircon to reduce load at high coolant temperature. Aircon is also deactivated when moving from a standstill and accelerating, so that maximum engine torque is sent to the wheels, no surprise that fuel consumption can be noticeably improved by not using aircon.
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