System Check
WARNING: This page is about a different car, the 1995 Mazda 929. However, it is still accessible from the selected car via links, so may be relevant.
Connect tachometer to engine. Start engine, and let idle. Shutter valve actuator rod should be extended at idle. See Fig 1 . Gradually increase engine speed to 5000 RPM and ensure actuator rod retracts. If system actuator does not operate as described, check for vacuum leaks. If no vacuum leaks are detected, check shutter valve and shutter valve solenoid.