Trouble code PO304

[jimwelsh]

Hello. I have a 1999 Ford Explorer XLT, and up until recently it was running fine. On Wednesday, 5/7, I got some gas at the local shell station, and by Thursday it was running like crap, as in missing, shuddering, lack of power, at which time the check engine light came on. I got home and connected my code reader, and it showed a PO304 code. I cleared the code. Today I went out and started it up, and it did not idle for more than 5 minutes before the check engine light came back on. Same engine running like crap, same PO304 code. I suppose my question would be, would some really bad gas cause this problem? That it might have gummed up an injector? Like I mentioned before, my Explorer was running fine until I got some gas at the Shell station. Any ideas? Any suggestions?
Thanks!

 

[Runnin'OnEmpty]

I would pull the plug and check it first. Might be
fouling out. Poor quality gas will build up deposits
on the plugs, but that happens gradually. Might be
the number 4 injector, but observing the plug will
tell a lot.

Check the number 4 wire too...

 

[jimwelsh]

Check engine light came back on today. This time when I hooked up my code reader I got the following:
Fault: 01
Pend: 01
PO304 01/02

 

[Turdle]

I would pull the plug and check it first. Might be
fouling out. Poor quality gas will build up deposits
on the plugs, but that happens gradually. Might be
the number 4 injector, but observing the plug will
tell a lot.

Check the number 4 wire too...