I have a 93 Dodge Dakota getting poor fuel mileage and black smoke out of the tailpipe. I've replaced the plugs, wires & air filter and hasn't made any difference. Starts & runs good, no pinging or knocking. Anyone have any ideas what to check next? Thanks!

 

O2 sensor

 

02 sensor. They recommend replacement every 80k miles I believe, but could be wrong.
Get it replaced asap so you don't plug the catalytic converter