Sounds like the Fuel Cut Solenoid (FCS) (aka ICS) to me too. Finding out is easy in theory, but be careful in practice. Bypass the entire Deceleration Fuel Cut System (shown in 1981 2F Emission Control Repair Manual, pg. 3-44) for this test by disconnecting FCS connector at carb and connecting 12v and ground jumpers to the two terminals on the FCS connector. Polarity doesn't matter, but BE CAREFUL not to touch the two jumpers to each other, they are close together. And, if using jumpers from truck battery, DON'T touch 12v jumper to the carb or obviously each other, it gets very exciting.
Better yet, make two short wires with female terminals on them to bring the male FCS connector terminals out of their housing and further from each other. Then hook up Pwr/Gnd jumpers--if FCS is working, you'll hear a 'click'. Start engine and see if behavior has changed/improved. An even more dramatic way to test is connecting those jumpers (brought out of the FCS housing) while engine is running, but that's DICEY to do with a running engine--do only if you're an experienced shade-tree. If the test result is the engine runs better (maybe with choke off now) with FCS jumpered to 'on', then the FCS is working properly. Now you have some Deceleration Fuel Cut System troubleshooting to do.
Better yet, make two short wires with female terminals on them to bring the male FCS connector terminals out of their housing and further from each other. Then hook up Pwr/Gnd jumpers--if FCS is working, you'll hear a 'click'. Start engine and see if behavior has changed/improved. An even more dramatic way to test is connecting those jumpers (brought out of the FCS housing) while engine is running, but that's DICEY to do with a running engine--do only if you're an experienced shade-tree. If the test result is the engine runs better (maybe with choke off now) with FCS jumpered to 'on', then the FCS is working properly. Now you have some Deceleration Fuel Cut System troubleshooting to do.
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