Long story bear with me..

Our old hunting truck had been sitting for about a year and a half and the gas in it smelled bad, so I siphoned it out of the truck (about 8 gallons) and decided the best way to get rid of it would be to put 4 gallons in each of the tanks on my 88 F-150 with the 4.9 I6 top it off and burn it. Well long story short it ran fine for about 100 miles, then started to spark knock some under load now its missing on 1 maybe 2 cylinders and running awful. I replaced the fuel filter already and that didn't change anything, but what ran out of it looked bad. I've burned one of the tanks and filled completely with fresh gas and some Berrymans B-12. Hasn't changed anything.

Did some trouble shooting today. I have 50psi fuel pressure at the rail both running and with the key on, which is right for the 4.9. Changed the plugs out, which only had a few thousand miles on them. All were dry and had an odd orange tint to them looked like varnish from the bad fuel. Ran the OBD I scanner on it and only faults were for EGR (been disconnected for years) and a code 44 'thermactor issue'. Changing plugs didn't affect how it was running at all. I'm thinking injectors are the only option left?

 

First get all the bad gas out of both tanks, we recently found out on my buddy's SuperDuty that sat for about a year. It only had about 2 gallons of bad gas in it, but not even 15 gallons of fresh fuel was enough to dilute it.

 

Just wanted to to update. I replaced the injectors and its running great now. I've never seen any actually get clogged before.