I have 2006 scion tc, my car has never giving me any problems until a couple of days ago the check engine light came on and it was flashing. I pulled over and turned it off. I was only 2miles away from home so I drove it. I put it on the code scanner and it said P0303 its s misfire cylinder 3. So I went and bought spark plugs for it. Changed them and then I started it and the check engine light is on but not flashing . It still Is running a little rough do I have to put my car back onto the code reader and reset it or what else should I do. So it either can be the coils or the fuel filter.