[1LowToy]

1984 you should have an O2 sensor on the exhaust and a computer behind the glove box. The carburator is wheat they call a feed back carburator. The oxegen sensor(O2 swnsor) is contently checking the exhaust gasses and feeding the info back to the computer. The computer is sending a signal to the mixture control solinoid in the carburator. It may be running rich due to a bad O2 sensor. See if you can pick up a good carb book of that erra. That carb is fairly expensive to get a rebuilt one but they are really not that complicated to rebuild. There is a voltage test that can be done to test the duty cycle of the mixture solinoid to see if it is within range. Does the truck have a check engine light on the dash?