Intake Air System

INTAKE AIR SYSTEM

Overview
The intake air system provides clean air to the engine, optimizes air flow, and reduces unwanted induction noise. The intake air system consists of an air cleaner assembly, resonator assemblies, hydrocarbon filter and hoses. The hydrocarbon filter trap helps 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 air intake system. The main component of the intake air system is the air cleaner assembly. The air cleaner assembly houses the air cleaner element that removes potential engine contaminants, particularly abrasives. The mass air flow (MAF) sensor is attached externally to the air cleaner assembly and measures the quantity of air delivered to the engine combustion chamber. The MAF sensor can be replaced as an individual component. The intake air system also contains a intake air temperature (IAT) sensor, which is integrated with the MAF sensor. The air induction resonator is a part of the intake air housing. The function of a resonator is to reduce induction noise. The air induction components are connected to each other and to the electronic throttle body assembly with hoses.

NOTE: For illustrations of intake air system components, refer to Fuel Delivery and Air Induction.

The overall quantity of air metered to the engine is controlled by the Torque Based Electronic Throttle Control (ETC) system.

Intake Manifold Runner Control (IMRC) Vacuum Actuated System

Vacuum Actuated Intake Manifold Runner Control (IMRC):

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.

The IMRC subsystem is used to provide increased intake airflow to improve torque, emissions and performance. The IMRC vacuum actuated system consists of a manifold mounted vacuum actuator and a PCM controlled electric solenoid. The linkage from the actuator attaches to the manifold butterfly plate lever. The IMRC actuator and manifold are composite/plastic with a single intake air passage for each cylinder. The passage has a butterfly valve plate that blocks 60% of the opening when actuated, leaving the top of the passage open to generate turbulence. The housing uses a return spring to hold the butterfly valve plates open. The vacuum actuator houses an internal monitor circuit to provide feedback to the PCM indicating the butterfly valve plate position.

On the initial engine start up the IMRC butterfly valve plates may remain open until the desired engine load and speed is reached. Once the desired engine load and speed are met, the IMRC vacuum actuator is energized which allows the manifold vacuum to close the IMRC butterfly valve plates. The IMRC butterfly valve plates open when the engine shuts off during a normal operation and close when the engine restarts.
1. The PCM monitors the throttle position (TP) sensor, cylinder head temperature (CHT) sensor, and crankshaft position (CKP) sensor signals to determine activation of the IMRC system. There must be a positive change in voltage from the TP sensor along with the increase in engine load and engine RPM at the proper engine temperature to open the valve plates.
2. The PCM uses the information from the input signals to control the IMRC electric solenoid based upon changes in the throttle position, the engine temperature, the engine load, and the RPM.
3. The PCM energizes the solenoid with the key on engine running. Vacuum is then applied to the actuator to pull the butterfly plates closed.

Throttle Body
Refer to Torque Based Electronic Throttle Control (ETC) for information on the throttle body. Description and Operation