Electronic Control Unit
The ECU consists of a microcomputer, inspection lamps, a diagnostic mode selector, an idle CO adjusting kit and connectors for signal input, output and for power supply. ECU has control of injected fuel amount, ignition timing, mixture ratio feedback, idle condition detecting, EGR operation, idle up operation, fuel pump operation, mixture heating, air injection valve operation and self-diagnosis.
The ECU calculates the basic injection pulse width by processing signals from the crank angle sensor and airflow meter. After receiving signals from each sensor detecting various engine conditions, the ECCS adds various pre-programmed enrichments to the basic injection amount. This ensures the optimum amount of fuel is injected into the intake manifold.
Conditions for fuel enrichment include during starting and warm-up, when accelerating or with a heavy load. Fuel mixture is leaned during deceleration in relation to closing speed of throttle valve. See Fig 1 .