1998 Dodge Ram Van 1500 Question: hesitates,popping noise, trying to get gas then goes along fine

the d code said it was o2 sensor, replaced the primary bank1 sensor1 still starts chugging along engine pops a bit when i pump gas pedal it will sometimes just start going again until i begin to slow down, when up to speed 50mph plus runs fine.Mechanics keep saying it could be a number of things how do i narrow it down to the actual problem