Variable Tumble Control System (VTCS) Delay Valve Inspection
WARNING: This page is about a different car, the 2003 Mazda Protege5, 2003 Mazda Protege, 2003 Mazda MX-5 Miata, 2003 Mazda MPV, and 2003 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.
Remove delay valve from VTCS shutter valve actuator vacuum hose. Blow air into port "A" air should flow out of port "B". Blow air into port "B" air should not flow out of port "A". If airflow is not as specified, replace VTCS delay valve.