Variable Induction System: Description and Operation

Intake Manifold Runner Control (IMRC) System

Note: In the Econoline Series, the IMRC system is used on the 4.2L engine only.

The intake manifold has two runners per cylinder feeding each of the intake ports in the cylinder heads, and improves engine performance using the Intake Manifold Runner Control (IMRC) system.

The IMRC housing assembly is located between the intake manifold and the cylinder head.
- It provides two air passages, one for each intake runner.
- One is always open and the other is switched from closed to open by means of a valve plate.
- Below 2800 rpm, the valve plate is closed to improve low speed and cold engine performance.
- Above 3500 rpm, the valve plate is switched open to improve high speed engine performance.

The valve plates are opened and closed by the IMRC vacuum actuators, which are controlled by the:
- IMRC solenoid
- Powertrain Control Module (PCM).

Below 2800 rpm:
- The IMRC solenoid is energized by the PCM, allowing vacuum to the IMRC vacuum actuators closing the valve plates.
Above 3500 rpm:
- The solenoid is de-energized and the vacuum holding the valve plates closed is vented, allowing the spring-loaded actuators to push the valve plates open.