I've got an 83 that idles up when hit throttle but takes few minutes if even goes back to idle. The cable goes back to its idle spot on top the motor. The past driver did fill with few gallons gas but that's well cleaned out. I've only got to look at it for few minutes.

 

The governor in the pump itself is going. Other words, gonna need a remand pump soon. Rosamaster pumps, that was my first hand at turning wrenches, and that's about all I did for the next 6 years.

 

Cutter, the cold idle solenoid might be sticking. I had an 83 that did the same thing. Try unplugging it and see if that helps