Intake Air Systems
INTAKE AIR SYSTEMSOverview
The intake air system provides clean air to the engine, optimizes airflow, and reduces unwanted induction noise. The intake air system consists of an air cleaner assembly, resonator assemblies, and hoses. Some vehicles use a hydrocarbon filter trap to help reduce emissions by preventing fuel vapor from escaping into the atmosphere from the intake when the engine is OFF. It is typically located inside the intake air system. The mass airflow (MAF) sensor is attached to the air cleaner assembly and measures the volume of air delivered to the engine. The hydrocarbon trap is part of the evaporative emission (EVAP) system. For more information on the EVAP system, refer to Evaporative Emission (EVAP) Systems. The MAF sensor can be replaced as an individual component. The intake air system also contains a sensor that measures the intake air temperature (IAT), which is integrated with the MAF sensor. For additional information on the intake air system components, refer to Engine Control Components. Intake air components can be separate components or part of the intake air housing. The function of a resonator is to reduce induction noise. The intake air components are connected to each other and to the throttle body assembly with hoses.
Throttle Body System Overview
The throttle body system meters air to the engine during idle, part throttle, and wide open throttle (WOT) conditions. The throttle body system consists of single or dual bores with butterfly valve throttle plates and a throttle position (TP) sensor. The airflow is measured by the MAF sensor.
The major components of the throttle body assembly include the TP sensor and the throttle body housing assembly. For additional information on the intake air system components, refer to Engine Control Components.
Features Of The Throttle Body Assembly Include:
1. A preset stop to locate the WOT position.
2. A throttle body-mounted TP sensor.
3. A coating sealant on the throttle bore and throttle plate makes the throttle body airflow tolerant to engine intake sludge accumulation. Some vehicles have a decal advising not to clean.
4. A non-adjustable stop screw for close plate idle airflow.
Overview Of The Intake Manifold Tuning Valve (IMTV) System
WARNING: Substantial opening and closing torque is applied by this system. To prevent injury, be careful to keep fingers away from lever mechanisms when actuated. Failure to follow these instructions may result in personal injury.
The IMTV is a manifold tuning device that affects the airflow volume of the manifold by connecting multiple plenums or inlets within the manifold system. The IMTV control valve is located in the center of the intake manifold away from the intake valve or cylinder head. The IMTV system does not have to be monitored for OBD II regulations.
This subsystem provides increased intake airflow to improve torque, emissions and performance. The overall volume of air metered to the engine is controlled by the throttle body.
The IMTV is a motorized actuated unit mounted directly to the intake manifold. For additional information on IMTV components, refer to Engine Control Components.
The motorized IMTV unit is not energized below a calibrated RPM. The shutter is in the closed position not allowing airflow blend to occur in the intake manifold. Above a calibrated RPM the motorized unit is energized. The motorized unit is initially commanded ON by the PCM at a 100 percent duty cycle to move the shutter to the open position, and then falling to approximately 50 percent to continue to hold the shutter open.
1. The PCM uses the TP sensor and CKP sensor signals to determine activation of the IMTV system. There must be a positive change in voltage from the TP sensor along with the increase in RPM to open the shutter.
2. The PCM uses the information from the input signals to control the IMTV.
3. When commanded ON by the PCM, the motorized actuator shutter opens up the end of the vertical separating wall at high engine speeds to allow both sides of the manifold to blend together.
