Can someone please help me . My girlfriend drove my car with a crack in the radiator . By the time I got it to the shop they said I overheated the engine . After I replaced the radiator it no longer overheats but it started knocking and back firing badly . I plugged it up to a machine and it told me I had a cylinder 3 misfire . I changed the spark plug but the problem never left . Can someone please help 🙏 ?