Intake Manifold Runner Control (IMRC) Vacuum Actuated 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 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.

Below approximately 3,000 RPM, the vacuum solenoid is energized. This allows manifold vacuum to be applied and the butterfly valve plates to remain closed. Above approximately 3,000 RPM, the vacuum solenoid is de-energized. This allows vacuum to vent from the actuator and the butterfly valve plates to open.

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 valve plates.
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.
The PCM energizes the solenoid with the key on and the engine running. Vacuum is then applied to the actuator to pull the butterfly plates closed.

Fig 1: Intake Manifold Runner Control (IMRC) Vacuum Actuated System
Courtesy of FORD MOTOR CO.