Fiat Punto car chucking when driving

i have a 04 fiat punto 1.2 8 valve, which has the engine light on and only doing about twenty miles to the gallon, took it to a mechanic he put it on the computer and the reading was (PO130 o2 sensor signal before cat) i remove the two sensors and clean them out, the engine light is no longer on but the car is still chucking when driving and only doing about 25 maybe a bit more miles to the gallon, so can anyone tell me why is the car still chucking and dose it need new sensors or could it be something else. thanks.