- air supply systems to engine cylinders;
- electronic control systems;
- fuel system.
The main element of the system is the engine control unit (PCM), which, based on information from many sensors, controls the fuel injectors by changing the pulse length, i.e. the period of time when the injectors are open. This ensures the preparation of a fuel-air mixture that corresponds to the required operating conditions of the engine.
The engine air supply system consists of an air filter, pipes, a throttle body, an idle speed control system, and an intake manifold. On models prior to 2001, the intake manifold and air distribution plenum are one unit.
Models produced since 2001 are equipped with a specially designed intake manifold with adjustable flow rate.
The throttle body is a pipe with adjustable air flow through it and serves only to control the amount of air supplied to the engine cylinders.
The lower part of the throttle assembly is heated by coolant to prevent it from icing in winter.
The adjustment screw is located at the top of the throttle assembly. The throttle position sensor is connected to the throttle shaft.
When the engine is idling, the air/fuel ratio is controlled by a control system that consists of the engine control module (PCM), the idle air control (IAC) valve, and other sensors (ECT, IAT, TPS, MAP, MAF), working in conjunction with the electronic fuel injection (EFI) system. The idle speed control (IAC) valve is activated depending on engine operating conditions (air conditioning system on, power steering operation, outside air temperature). This valve regulates the amount of air supplied to the engine cylinders bypassing the throttle valve. Thanks to this, when the engine warms up, even with the throttle valve closed, air enters the engine cylinders, regulating the idle speed. The intake manifold also reduces airflow pulsations.
The electronic control system controls fuel injection, spark advance, diagnostic system and other systems.
The fuel system consists of the following components:
- fuel pump;
- fuel pressure regulator;
- fuel filter;
- fuel lines;
- fuel distribution line;
- injectors.
On models before 2001, two fuel filters are installed: the main one is on the left side of the engine compartment, and the additional one is in the fuel pump/fuel level sensor block.
On 2001 and later models, there is 1 fuel filter installed in the fuel pump/fuel level sensor unit.
The injectors dose and atomize the fuel. When voltage is applied to the solenoid coil, the needle rises, allowing fuel to pass through. The amount of fuel is determined by the pulse duration during which the injector is open.
The fuel pump main relay is located in the engine compartment relay/fuse box and is controlled by two electrical circuits. The first circuit is controlled by the engine control unit (PCM), and the second by the ignition switch. If the engine fails to start after the ignition is turned on, the PCM will deactivate the fuel pump relay after 2 seconds. Subsequently, when the engine starts, the relay activates the fuel pump after the first pulse from the camshaft position sensor.
[The material is republished from an online website: ToyotaMAN.ru]