Fiat Stilo sometimes does not throw me ...

Good I just changed the water pump because I was annoyed and the distribution strap because I reached 100.00 km I made the change of oil and filter, but the car gives me a problem these last days when I reach a round or brake when putting first or second can that be? Tmb Buy the liquid that to clean the injection but I do not think it serves as much, it is diesel the car, thanks