Decel Valve

The Decel Valve is behind the air cleaner, and is situated between the large manifold vacuum fitting on the back of the carburetor and the upstream Pulse Air tube. When you take your foot off the gas and decelerate, manifold vacuum soars, actuating this valve and opening it. This allows the manifold to draw fresh air in below the carburetor. It's a pollution control thing.

If this valve should leak or stick open, the result would be a massive air leak into the manifold, driving the computer crazy.

For a quick and easy test, remove the air cleaner lid. Put your finger on the upstream Pulse-Air tube inside the air cleaner. Raise the RPMs some and then close the throttle quickly. You should feel strong vacuum for a moment, then you should hear a distinct "thunk" from the upstream Pulse-Air tube as the open Decel Valve slams shut and the strong vacuum disappears. If noise from the Pulse-Air tubes themselves is interfering, you can temporarily disable them by pulling the vacuum lines off the air valves just above the check valves.

Decel Valve

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