Cutlass Supreme V6-204 3.4L DOHC VIN X SFI (1995)
Upper Intake Manifold: Description and Operation
Upper Manifold Assembly
The upper manifold assembly is a single casting that integrates the intake plenum and the throttle body. The throttle valve is used to control air flow into
the engine, thereby controlling engine output. The valve is opened by the driver through the accelerator controls. During engine idle, the throttle valve is
almost closed, and air flow control is handled by the Idle Air Control (IAC) valve described later. To prevent throttle valve icing during cool weather
operation, engine coolant is circulated through a passage in the upper manifold assembly near the throttle valve. Vacuum ports are located at, above, or
below the throttle valve to generate vacuum signals needed by various components.