1987 Daihatsu Charade Smoking and idling problem

My car is daihatsu charade. It started producing smoke which smell like fuel. It is also idling by itself. The carburetor is clean. The spark plugs are ok. It has strength an speed. The problem is just smoking and idling high. When I adjusting the idling screw, the idling goes down and then comes back after driving for about a kilometer or two.
What could be the problem? Kindly help.

Peter