Cutlass Ciera L4-2.2L VIN 4 (1995)
Intake Air Plenum: Description and Operation
Intake Manifold Assembly
Lower Manifold Air Flow
INTAKE MANIFOLD ASSEMBLY
The intake manifold is made up of the upper and lower manifold assemblies.
Upper Manifold
The upper manifold assembly is a single casting that includes the upper portion of the air chamber (plenum) and the air inlet (fitted with a throttle
valve). This assembly replaces the individual throttle body assembly and plenum components. The throttle valve is used to control air flow into the
engine, thereby controlling engine output. The throttle valve is opened 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. Vacuum ports located at, above, or below the throttle valve
generate vacuum signals needed by various components. The nonadjustable, throttle shaft-driven, Throttle Position (TP) sensor is attached to the