Air intake system
The air intake system consists of an air filter, an intake air line, resonators, a throttle body and an intake manifold. Resonators are specially shaped chambers mounted on the intake air duct. They work as storage drives or receivers to help «calm down» air flow through the intake duct. Replacement procedures for all of these items are covered in this chapter (with the exception of intake manifolds, the work of which is described in chapter 2A or 2B).
Throttle body on 1999-2003 models
Throttle body on 2001-2003 models with a four-cylinder engine has a conventional design with a single channel. The lower part of the throttle body is heated by engine coolant to prevent icing of the body in cold weather. A throttle position sensor is installed on the damper axis (TR), which allows you to control changes in the throttle opening angle. An idle speed control valve is connected to the underside of the throttle body (ISC). For information about the TP sensor and ISC valve, refer to chapter 6.
Throttle body on medals 1999-2003 with a V6 engine is a dual port design that includes a three-stage variable geometry intake system (ACIS). Similar to the single port throttle body used on four-cylinder models, the dual port throttle body used on V6 models is also equipped with a throttle position sensor (TR) and idle speed control valve (ISC). For more information about the ACIS system, TP sensor, and ISC valve, refer to chapter 6.
When the engine is idling, the ratio «air is fuel» controlled by idle speed control system (ISC). The ISC system includes an engine coolant temperature sensor (EATING), air intake temperature sensor (IAT), throttle position sensor (TR), mass air flow sensor (MAF), various other sensors, powertrain control module (RSM) and ISC valve. The ISC valve is activated by the PCM under certain conditions, such as cold cranking or when the engine is under power steering at low vehicle speeds or when the A/C is turned on. The ISC valve controls the amount of air that bypasses the throttle and enters the intake manifold. For more information about the ISC valve and the ISC system, refer to chapter 6.
Throttle body on 2004 and later models
The throttle body on 2004 and later 4-cylinder and V6 models is equipped with ETCS-i electronic throttle control. The single port throttle body on these models is electronic, meaning it does not use an accelerator cable to open and close the throttle. Instead, a DC motor is installed that opens and closes the throttle inside the housing in response to a command from the powertrain control module (RSM). The PCM monitors the position or angle of the accelerator pedal using the accelerator pedal position sensor (APP), then commands the DC motor inside the throttle body to appropriately open or close the throttle. This throttle body is equipped with a throttle position sensor (TR), but, unlike earlier blocks, the sensor is an integral part of the throttle body and can not be removed. On such units, the idle speed control valve (ISC) absent. The idle speed control function is controlled by the PCM. For more information about the ETCS-i, APP and PCM sensors, refer to chapter 6.
Electronic control system
Information sensors, powertrain control module (RSM), downstream actuators and various emission reduction systems used on these vehicles are described in chapter 6.
Fuel supply system
The fuel delivery system includes the fuel pump, fuel pressure regulator, fuel filter, fuel lines, pressure pulsation damper, fuel rail and fuel injectors. The fuel pump built into the tank is an electric in-line pump. Fuel is drawn into the pump through the intake strainer, passes through the pressure regulator, through the fuel filter, and is delivered to the injectors. The fuel pressure regulator maintains a constant pressure in the injectors.
Nozzles - with electromagnetic drive, constant stroke, needle type. They consist of an electromagnet, a plunger, a needle valve and a housing. When current is applied to the solenoid, the needle valve disengages from its seat and a pressurized jet of fuel exits the nozzle body through the atomizer. The cyclic supply depends on the duration of the pulse, that is, the period of time during which the needle valve is open, this period of time, in turn, is determined by the period of time during which current is supplied to the electromagnet. Since the injection advance of the injector determines the opening and closing intervals, which in turn determine the ratio «air is fuel» injected mixture, the injector injection advance must be very accurate.
The EFI main relay, located in the fuse/relay box in the engine compartment, supplies power to the fuel pump relay (opening relay) through the ignition switch. The PCM controls the ground signal suppressed to the fuel pump, responsive to the start signal and camshaft position signals at start.