Intake Manifold Runner Control (IMRC) Vacuum Actuated System

The IMRC vacuum actuated system consists of a manifold mounted vacuum actuator and a PCM controlled electric solenoid. For additional information on IMRC vacuum actuated components, refer to ENGINE CONTROL COMPONENTS . 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 a large percentage 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.

The vacuum solenoid does not energize below 3,000 RPM, allowing the manifold vacuum to be applied and the butterfly valve plates to remain closed. The vacuum solenoid de-energizes above 3,000 RPM allowing the vacuum to vent from the actuator and the butterfly valve plates to open.

1. The PCM monitors the TP sensor, CHT, and CKP 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 RPM at the correct engine temperature to open the butterfly 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, and the RPM.
3. The PCM energizes the solenoid with the ignition on and the engine running. Vacuum is then applied to the actuator to pull the butterfly valve plates closed.