1991 Chevy Lumina seems to be flooding its self out.

Engine Performance problem
1991 Chevy Lumina 6 cyl Front Wheel Drive Automatic 165k miles

I have a 91 lumina and it will stall while driving down the street or stop or in park I noticed when it does this there is black smoke which I am beleiving to be getting to much fuel, it only does the when its running funny engine lite comes on I jumped the connection to get code but dont get no code just the 12 code keeps going. I had same problums last summer with car no problums all winter even on long drives and stuff then warmer weather comes and gettin problums back I get a avg. Of about 18 miles a gallon also been sense I got the car fuel filter has been replaced also when it starts runnin like that when I am at like 50mph it kicks the rpms up to about 2200 from bout 1700 and and smells like gassy fumes can some one please help me I kinda like the car but even if I didnt I cant afford a new one at the moment. Thanx