I have a 94 civic ex that is getting around 20mpg. I'm getting a CEL with code 43, I replaced O2 sensor, distributor, rotor, cap, wires, plugs, injectors, pcv valve. Any ideas what could be causing the code or what could make it run rich and smell raw fuel plus black smoke, also started to backfire when i let off the gas in 3rd or 4th gear.

 

i'm not familiar with that code.

35mpg to 20mpg caused O2 sensor and injectors.

 

You'll want to run a diag on your entire fuel system in order to pinpoint the problem. Hope you get it fixed.