I got a 1999 ford expedition and these are my issues: filled up with gas drove about 200 miles and expedition started to miss very bad and check engine light was flashing. Started with new spark plugs, didn't fix. when I had it scanned no codes came up except the on for the check engine light, but the left bank down streamO2 censor was not as responsive as the others so I replaced it. I have checked the injectors and the COP's (coil over plug) they where good .The fuel pressure is 35 psi, the fuel pressure regulator is making a differance when dissconected. The tank was drained to within about 1/16 of a tank then filled with 91 octaine and lucas injector cleaner and fuel conditioners was added.

If anyone can help
Thanks: Crazyman

 

After replacing all of that, did you try to clear the codes? Sometimes clearing codes helps, and if it doesn't work it may then give you a new code to work from.