Intake Air Bypass (IAB) Control System

Intake Chamber Volume Control System:

NOTE: This section addresses the mechanical components of the CHAMBER VOLUME CONTROL SYSTEM. For information regarding vacuum solenoid controls, refer to COMPUTERIZED ENGINE CONTROLS.

1. Apply vacuum to the high and low control diaphragm assemblies. If either diaphragm fails to hold vacuum, replace the diaphragm assembly.
2. Start engine and allow to idle.
3. Check for vacuum at high and low vacuum control diaphragm assemblies. Both hoses should show manifold vacuum. If no vacuum is present at either hose, refer to COMPUTERIZED ENGINE CONTROLS.
4. Raise engine speed to 3300 RPM. Check for vacuum at the low diaphragm vacuum hose. No vacuum should be present.
5. Raise engine speed to 4000 RPM. Check for vacuum at the high diaphragm vacuum hose. No vacuum should be present.
If vacuum is present during test 4 or test 5, refer to COMPUTERIZED ENGINE CONTROLS.
6. Check the bypass control linkages and shafts for binding, sticking, or excessive wear. If linkages do not operate smoothly, disassemble and clean the bypass assembly.