Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Intake Manifold Runner Control (IMRC) Vacuum Actuated System
The IMRC vacuum actuated system consists of a manifold mounted vacuum actuator and a PCM controlled electric solenoid. 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 proper 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.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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