Fiat Punto Is Mis-fireing

Happy New Year to everyone...! I would like to know if this can be solved..I jacked up my 1996 Punto from the back to adjust my rear brakes, had to leave it jacked up because the night caught up with me, anyway woke up the next morning frost was all over the car I fixed the brakes then decided to start the car, as I attempted to turned the engine over I heard a scraping noise from the engine (this is still while the car was jacked up), I managed to start the car anyway but then noticed that the Engine was missing very badly, black smoke was coming from the exhaust and all, I have not being able to get the car to run properly since then even after I've tried putting Red-X in the petrol tank, can anyone tell me what could be the problem..!