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One more thing to check is the Decel Shut-off valve. It is a cylindrical shaped valve below the Inlet Manifold. The pipe from the top of the Air filter connects to it. a small vacuum pipe comes from it and connects to an electrical valve on the left front fender. If you remove this pipe during idle, and you suck on it, the engine should stop. If it does not, the valve is probably shot. It operates on the micro switch next to the throttle that senses when your foot is off the pedal.

The principle of this system is that when you take your foot off the pedal at speed, high vacuum in the lower intake manifold opens the air valve, allowing air from the air cleaner directly into the lower intake manifold, bypassing the upper intake manifold's fuel sensor plate and throttle. The resulting absence of vacuum in the upper intake manifold makes the fuel sensor plate return to its idle position, cutting off most of the fuel. The un-throttled rush of air into the cylinders also decreases pumping losses. The electrical switch is to ensure the valve only opens during deceleration/overrun, not at idle. If you connect the air valve directly to high manifold vacuum at idle, the engine should die. If it doesn't, the air valve may not be working or some adjustment may be off, or there may be a vacuum leak. You can live without this system, but your fuel consumption will be higher by 20% or more.
How would this operate sir? I tried to follow what you explained here but the switch over valve that is operated by the microswitch is energized whenever I take my foot off the pedal (How should it differentiate between idle and deacceleration)

By the way, I don't know where to connect the decel valve vacuum control, should it be full vacuum or ported? is there difference between the vacuum port right of the intake or the one on the throttle?

thank you in advance.
 
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