Deceleration Valve: Testing and Inspection

Deceleration Valve:

1. Connect a tachometer, start engine and allow idle to stabilize.
2. Remove the manifold vacuum source from the deceleration valve (small hose).
3. Reconnect the hose removed in step 2 above and listen for air flow through the ventilation pipe and into the deceleration valve. The idle speed should also drop when the vacuum hose is reconnected.
4. If air flow does not continue for at least 1 second or the idle rpm does not drop considerably, check vacuum hoses going to deceleration valve for restrictions or leakage.
5. If ok replace the deceleration valve.