Intake Manifold Runner Control (IMRC)
An electronic or vacuum actuator that opens and closes butterfly valves in the intake manifold to optimize airflow.
The Intake Manifold Runner Control (IMRC) system is a performance-enhancing mechanism used to vary the airflow path inside the intake manifold. At low engine speeds, long, narrow intake runners are ideal for building air velocity, which improves torque. At high engine speeds, short, wide runners are needed to maximize airflow volume for peak horsepower.
The IMRC system features butterfly valves inside the intake runners, controlled by an electric actuator motor or a vacuum solenoid. The ECU controls the actuator, opening or closing the valves depending on engine RPM, throttle position, and engine load.
If the IMRC valves become sticky due to carbon buildup, or if the actuator motor fails, the engine will suffer from poor throttle response, loss of low-end torque, or decreased high-RPM power. A failed IMRC system will illuminate the check engine light and store diagnostic codes such as P2004 or P2005.