The Electronic Fuel Injection system consists of three basic subsystems.

• The electronic control system determines basic injection quantity based upon electrical signals from the air flow meter and engine rpm.

• The fuel delivery system maintains a constant fuel pressure on the injector. This allows the ECU to control the fuel injection duration and deliver the appropriate amount of fuel for engine operating conditions.

• The air induction system delivers air to the engine based on driver demand. The air/fuel mixture is formed in the intake manifold as air moves through the intake runners.

The EFI system allows for improved engine performance, better fuel economy, and improved emissions control. Although technologically advanced, the EFI system is mechanically simpler than other fuel metering systems and requires very little maintenance or periodic adjustment.

• The Conventional EFI system only controls fuel delivery and injection quantity. 'Me introduction of EFI/TCCS added control Of Electronic Spark Advance, idle speed, EGR, and other related engine systems.

• Most of Toyota's late model EFI systems are equipped with some type of on board diagnosis system. All TCCS systems are equipped with an advanced self diagnosis system capable of monitoring many important engine electrical circuits. Only some of the later production Conventional(P7) EFI engines are equipped with a self diagnosis system.

Reprinted with permission from Toyota Motor Sale, U.S.A., Inc. from #850 EFI Course Book.

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