I've got a 2004 Mustang V-6. It was running perfectly fine last Friday and then I filled up with gas (87) and it started sputtering slightly. The check engine light came on on Saturday, so i had the code checked and it was OBD II-302 (misfire on cylinder 2). I replaced all the plugs and plug wires. This seemed to have fixed the problem until I filled up again (this time with 93), and the sputtering came back, as well as the check engine light (OBD II-304 this time). It still runs good, but when i get on the accelerator hard it starts sputtering a little. I'm hoping this is just a case of bad gas. Any other ideas of what the problem is?

 

I was thinking bad fuel injector or a cylinder going bad. Do a compression test or check your injectors or both

 

Why are you changing gas? Instead of eliminating variables, you're creating them. Be consistent, and go from there...

 

So I should've got the same gas that seemed to have caused the problem in the first place?

 

Buy gas from a reputable station, and buy the octane that your car is tuned for.

 

Ignition coil pack

 

+1 on the ignition coil pack... bad gas would not cause a misfire in one specific cylinder. The fact that it is jumping around from #2 to #4 points to the coil pack as well, IMO.