general problems of the 1996 Ford Taurus

I recently brought the car for 4,00 and some change a bout a year ago two days after I brought it the check engine light came on and every now and then while driving it would cut off I took the car back to the place I brought it from and told them they told me to bring it back in I would have to leave it so I got some one to follow me and take me back home when I went to pick up the car it was running but by the time I got home the check engine light was back on. Then the defrost didn't work I took it back to them. That's when the air condictioner stop working I just quit complain the car ran pretty smooth although the check engine light stayed on . I went to start my car one night and it wouldn't start so I went and brought so heet I thoght because it was cold out side it is winter I begin hear a hiss llike some air is excaping from somewhere under the hood but yo hear it inside the car like a lot of static. It time for me to get a tuneup now the car really runs sluggish and turns off more often and you can't turn the wheels so that is spooky I had the check light checked out and they said it was my lean sensor too much air is getting into the gasoline and that has something to do with the catalyic converter.