2002 SuperCrew 5.4 I filled up with gas about a week ago and then after about 30 miles or so it started surging under light load/throttle. I progressively got worse the next day. I thought it may have been bad gas so I dumped a couple bottles of HEAT I had on the garage in case it had water in the gas. No difference...I added a bottle of STP complete fuel system cleaner. Seemed that as the gas tank got closer to empty it slowly improved, once I was down to about 1/4 tank it was almost gone. I ran it close to empty and filled up yesterday morning and it was back bad as ever? The truck does need plugs I'm sure as they have about 111,000 on them but up until last week was running very good and getting decent mileage and when the tank was almost empty it seemed to run almost normal with and occasional surge now and then ? Doesn't really make sense for it to be plugs, coils, injectors, etc. since they would be bad no matter how much gas was in the tank. Any ideas ?

Thanks,
Scott

 

Any ideas ?

so far no CEL...it has been driven 300+ miles since the surge/misfire started. Could a failing fuel pump cause these symptoms...or partially clogged fuel filter? full tank of gas runs like crap...1/4 tank and less seems to improve and run almost normal?

thanks,
Scott