Engine Performance problem
1992 Cadillac Deville V8 Front Wheel Drive Automatic 140000 miles

When cold or first started the engine runs great no misses, smooth idle the car drives fine for about 1/2 mile then starts sputtering missing out and dies won't re-start until cold.
have replaced many components and am running out of ideas.
the only thing Have not replaced the ox- sensor mostly because I cant get it out.
but if the car fails after the os works could it be the ecm? the only code i get is that the batt has been disconected (sorry don't remember the #)