Ford Repair: 2003 expidition 4.6l 85000mi, oxygen sensor, dual heat

Question
this afternoon the truck started running rough and misfiring.i pulled the codes @ a local auto parts store. they are 204,171,304,316.I filled the tank last night @ a store I normally don't use.The truck had been running fine no codes or problems prior to this event.could this be caused by bad gasoline, if so what course of action would you recommend?  

Answer
Brian,

Code 204 is injector circuit malfunction. This means the computer is not getting power back from the #4 injector. Now #4 is passenger side all the way back. I mean way back. They are a pain to access, but the heater hose (esp if you have dual heat) tend to rub the plug there. So first step is make sure it is plugged in and the wire is not broken.

Code 171 is Bank 1 running too lean. This is caused by injector #4 not firing. It is on bank #1. #4 cylinder will continue to pump oxygen into the exhaust and force the oxygen sensor to go lean.

Code 304 is cylinder #4 misfire detected. No surprise right?

Code 316 I have no listing for so I assume it too be a Ford specific code probably related to the misfire.

So the moral here is check that last injector on the passenger side. Maybe the plug came off. never know.

I hope that helps a bit. Let me know what you find.