coughing

Hi was wondering if anyone can help.. Car running rough, coughing then back firing, tried replaced sparks, temperature and air sensors still spluttering into life after revving engine... Anyone got a clue????:shrug:

Few days ago when my car was cold it would cut out as soon as it got to where it should be idling. this went away after a few days but now i have a differnt problem. throughout the rev range, even when warm, the car is coughing. its like a small backfire type noise. the revs are no longer smooth...