Hey everyone, just throwing this out here to see if anyone has a clue. I got a04 f-150 lariat 4x4 5.4 3v. That has developed an intermittent miss and or backfiring during hard accelerating, also misses when getting on the highway going over 65 mph and I've noticed that it does it mostly when overdrive kicks in. I've changed the plugs, coils, recently. Any help will be greatly appreciated!

 

Check your fuel pump driver. Or clean your maf

 

Maf? Where would the fuel pump driver be located and how would you check it? Thanks for your reply!

 

maf is the mass air flow sensor, the pump driver should be under the car on one of the frame rails near the back of the truck

 

you can find the location online for the driver

 

Thanks again I'll keep picking at it and post results....although the plugs and coils make it run a lot better but didn't resolve the problem....I was kind of thinking is sound like s potential vacuum leak also.....well see

 

check you vacuum lines and rubber elbows. had the same problem. turned out to be a broken line. my buddies 97 had the same problem. turned out to be an elbow.

 

Clogged cat...........

 

The FPDM (fuel pump driver module) is located under your spare tire attached to the frame rail. If it is corroded, change it out. That might solve your misfiring. The FPDM can cause an extensive list of problems.

 

when ours went bad we thought it was the fuel pump, glad we checked this first, indeed if it is corroded and all messed up swap it out. It can cause the truck to just die- dead .