Intake Manifold Swirl Control Vacuum Actuated System - 2.3L (VIN D)
Intake Manifold Swirl Control (IMSC) vacuum actuated system consists of manifold mounted vacuum actuator and Powertrain Control Module (PCM) controlled electric solenoid. See Fig 1 and Fig 2 . PCM monitors Throttle Position (TP) sensor, cylinder head temperature sensor and crankshaft position sensor signals to determine activation of IMSC. A positive change in voltage from TP sensor along with increase in RPM at proper engine temperature must be present to open valve plates. When conditions are met to open valves, PCM energizes IMSC solenoid and vacuum is then applied to actuator to pull butterfly plates open.
Linkage from actuator attaches to manifold butterfly plate lever. IMSC actuator and manifold are a composite/plastic with a single intake air passage for each cylinder. The passage has a butterfly valve plate that blocks 60 percent of intake opening when actuated, leaving top of intake passage open to generate turbulence. A return spring is used to hold butterfly valve plates closed. Vacuum actuator provides feedback to PCM indicating butterfly valve plate position.
When engine speed is less than 3000 RPM, vacuum solenoid will be energized to allow manifold vacuum to be applied and butterfly valve plates will remain closed. When engine speed is 3000 RPM or more, vacuum solenoid is de-energized to allow vacuum to vent from actuator and butterfly valve plates will open.