My 2004 F150 misses at around 2000 rpm but quits once you go under it or over it. At first we thought it was gas. We got it to shoot a code out so we took it auto zone and let them read it and they said its backfiring in all cylinders they said it was gas. So we put some HEET in it and filled up with good gas and it done better then what it was so we went with it.

It started back so we changed the fuel filter and there was water and some kind of junk in there so we fixed that and put a full take of a good gas in it and it didnt do it today until i was headed home from work. What is the problem

 

What were the codes?

That would help out a lot.........

 

You probably have so much crap in the gas tank that you may need to drop it, drain it, and clean it out.

 

I read a post on here about the COP's not having any di-electric gease on the springs might want to try that, would be a pretty easy fix