Air Intake System Description. Pontiac Vibe

For 1990-2009 cars only

Makes 🢒 Pontiac 🢒 2008 🢒 Vibe - FWD 🢒 Engine 🢒 Engine Controls and Fuel - 1.8L (LV6) 🢒 Air Intake System Description

The air induction system provides air and oxygen for the combustion process. The air cleaner (ACL) keeps dirt from entering the engine. Outside air is drawn into a forward mounted air cleaner. The air first passes through a carbon filter (3) that is located in the upper ACL housing (1). The carbon filter absorbs fuel vapors that may be emitted from the combustion chamber after the engine is turned off. Next the intake air flows through the air filter element (2) and past the mass air flow (MAF) sensor to the throttle body. The air then flows through the intake manifold and into the cylinder head. Finally in the cylinder head, the air travels through the intake runner, ending in the combustion chamber.

The following components are directly or indirectly a part of the air supply system.

Mass Air Flow (MAF) Sensor


(1)	Mass Air Flow (MAF) Sensor
(2)	Platinum Hot-Wire Element
(3)	Intake Air Temperature (IAT) Sensor Thermistor

The mass air flow (MAF) sensor (1) measures the changes in the intake air volume that result from the changes in throttle opening and the air density. The airflow measurements are used by the PCM in order to determine the engine fueling requirements.

The MAF sensor is a hot-wire design. A platinum hot-wire (2) and a thermistor (3) are located in the intake air bypass passage of the MAF sensor housing. The temperature of the platinum hot-wire is affected by exposure to air flow and by exposure to air temperature. The platinum hot-wire is maintained at a set temperature by controlling the current flow through the wire. The MAF sensor converts the changes in current flow to a voltage signal. The voltage signal from the MAF sensor enables the PCM to detect changes in the air density and changes in air volume.

The MAF sensor also contains the IAT sensor. The IAT sensor cannot be serviced separately from the MAF sensor.

Intake Air Temperature (IAT) Sensor

The intake air temperature (IAT) sensor is an integral part of the mass air flow (MAF) sensor that is mounted in the air cleaner assembly. The IAT sensor measures the temperature of the air entering the intake manifold. The IAT sensor provides temperature information to the circuitry of the MAF sensor and the PCM.

The IAT sensor is a thermistor--a resistor whose resistance changes as a function of temperature. When the temperature is low, the resistance is high. The resistance decreases as the temperature increases. The IAT sensor is a 2-wire circuit with a reference or signal voltage and a ground coming from the PCM.

IAT Sensor Operation

Temperature	Resistance	Voltage
Low	High	High
High	Low	Low

Throttle Body Assembly

The throttle body contains the throttle valve that controls the amount of air entering the engine. The throttle valve is controlled electronically by the throttle actuator control (TAC) system. Some of the features of the throttle body with the TAC system are the following:

•	An electric motor opens and closes the throttle valve.

•	The throttle valve is spring loaded and the default position is slightly open.

•	The throttle position (TP) sensors are integral to the TAC module assembly.

•	The TAC module is an integral part of the throttle body assembly.

For more information on the TAC system, refer to Throttle Actuator Control (TAC) System Description.