System Operation

When engine RPM is less than about 3200 RPM, a signal from the PCM energizes the by-pass low and high control solenoid valves allowing vacuum to low and high IAB control diaphragms. When vacuum is applied to low and high diaphragms, IAB control valves inside manifold close, causing a long intake path.

When engine speed is about 3400 RPM, PCM deactivates by-pass low solenoid valve, cutting vacuum to low IAB diaphragm, causing intake air to go through both long and medium intake paths. At engine speeds greater than 3900 RPM, the PCM switches off both solenoid valves, and intake air goes through all 3 intake paths.