Toyota Repair: Black Smoke, sorry bro, engine managment

Question
My '92 pick-up is blowing black smoke from the tailpipe when it's idling, but I am told that it disappears when I accelerate.  What could be causing this?

Answer
hi dave, this is very rich fuel(unburned fuel) sorry bro but it is so many things that can cause that. for exhample
ignition system problem(secodary) plugs wires cap rotor, fuel presure, carburator if you have one engine managment
it needs to be checked.