| Re: 4.6 modular The IMRC system has two intake manifold runners per cylinder for air flow into the combustion chamber. One runner is always open and the other is commanded open by the Powertrain Control Module (PCM). Below approximately 3000 rpm, the valve plates are closed and above approximately 3600 rpm, the valve plates are opened. The PCM also receives a signal from the IMRC system indicating valve plate position. The quantity of air metered to the engine is controlled by the throttle body assembly.
The IMRC system also has a housing and actuator assemblies. The IMRC housing assembly is an aluminum casting with two air intake passages for each cylinder. One passage is always open and the other is opened or closed with a butterfly valve plate. The IMRC Actuator is either a remote mounted electro-mechanical control actuator or a direct mounted vacuum actuator type system. In the remote system, the IMRC housing valve plates are held closed with a return spring located on the valve plate shaft. When commanded open by the PCM, the IMRC actuator pulls on the IMRC shaft assembly using an accelerator type cable. On the direct mounted vacuum actuator system, the return springs are located within the vacuum actuator. The PCM commands a vacuum control solenoid allowing the vacuum to pass to the vacuum actuator drawing the valve plates closed or releasing the vacuum allowing the actuator to push the valve plates open. Substantial opening and closing torque is applied in both systems. Care should be taken to keep fingers away from the lever mechanisms when actuated. It also provides a switch signal to the PCM for the plate position. This is the decription given in the ford service manual, Roy |