For 1990-2009 cars

(1) | Fuel Injector Cover
(2) | Fuel Injector
(3) | Upper O-Ring (Large)
(4) | Fuel Pressure Regulator
(5) | Upper TBI Assembly
(6) | Lower O-Ring (Small)
(7) | Vacuum Port
(8) | Throttle Valve
(9) | Lower TBI Assembly
(10) | Idle Speed Control Motor

The function of the fuel metering system is deliver the correct amount of fuel to the engine under all operating conditions. Fuel is delivered by the fuel injector in the throttle body fuel injection unit. The fuel injector is controlled by the powertrain control module. The powertrain control module bases the control of the fuel injector on several important engine parameters. These engine parameters include the following:

• | The Manifold Absolute Pressure (MAP) Sensor

• | The Intake Air Temperature (IAT) Sensor

• | The Engine Coolant Temperature (ECT) Sensor

• | The Throttle Position (TP) Sensor

• | The Heated Oxygen Sensor (HO2S)

• | Engine Speed (RPM)

Determining air density is critical to proper air/fuel management. Air density is primarily derived from the IAT sensor and the MAP sensor inputs. The IAT sensor measures the temperature of the air that is entering the engine. The MAP sensor measures the air pressure in the intake manifold. When the intake manifold pressure increases, the air density in the intake manifold also increases, requiring additional fuel. The information from the IAT sensor and the MAP sensor is used by the PCM to calculate air density and modify fuel injector pulse width.

The fuel metering system consists of the air/fuel delivery system and the electronic control system. This section covers the air/fuel delivery system. For information on the electronic control system refer to Powertrain Control Module Description and Information Sensors/Switches Description .