i have a 2001 v6 cougar and if i do not have a full tank of gas it will almost buck i change plugs and wires and i have no clue how to describe it but the car bucks almost it will cut out then grab really hard

 

sounds like it''s flooding. A bad oxygen sensor could do that. usually by that stage it''s throwing codes and the check engine light should be on. Clogged fuel filter could also do that. clogged fuel injectors could do it too. I''d change the fuel filter and run some fuel system cleaner through it. if it''s throwing codes, have them read cause it''s prolly a bad sensor. If no codes, it''s probably the fuel filter.