93 zj rough runnin

[85zebracherokee]

My wife drives a 93 5.2 zj and every once in a while it will start running rough
and while in the mid to upper rpm ranges will beltch black smoke. Checked sensors per the factory service manual and could't find anything. Also checked for code and got an oxygen sensor but about half a million different problems could set that code. Any ideas????????

 

[90Xjay]

is there just one O2 sensor on that model?

 

[85zebracherokee]

Ya one o2 behind the y pipe before cat.