Mark Viii Ford Crown Victoria I

Each cylinder features 2 intake runners located between intake manifold and cylinder head. The primary runner feeds air to the cylinders whenever engine is running. The secondary runner is opened and closed by the IMRC vacuum actuator, which is controlled by the IMRC solenoid and Powertrain Control Module (PCM). With engine speed less than 3000 RPM, IMRC solenoid is energized by the PCM allowing vacuum to the IMRC vacuum actuator, closing the secondary runner. With engine speed more than 3000 RPM, solenoid is de-energized and vacuum is vented, allowing actuator to push secondary runner open. This system improves low and mid range torque, and improves fuel efficiency.