I have a 04 600HO engine that misses or backfires every once in a while, usually after a fill-up.
I have used fule from differant sources. Chevron, Shell, Safeway, or Terxaco etc. The truck has 17K is automatic, if that means anything.
Are there great differances in the fuel? I am not the mechanic type and could assume things all day. Any suggesions from anyone? Any clues would be helpful. Thanks....Tom

 

Make sure filter is ok(replaced at 15k) then take in in if still doing it.Possable injector bad.

 

backfires? I usually associate that with a loud shotgun like bang. If that's the case, take it in.

If it just misfires with smoke and a little noise, you still need to take it in and document it if anything. Probably injectors, but you may need a reflash depending on your build date (on engine vanity cover sticker). Maybe both.