thanks in advance for any help you may be able to give me. so here it goes to start it off I have a completely stock (except for a flowmaster muffler) 2008 f150 4x4 crew cab xlt with 55k miles. the problem im having is that my truck for sum reason seems to not want to go above 3k rpms when I hammer it. after I get around 50 mph they slowly go up. in result my truck is accelerating very slow anywhere between 14 to 19 seconds to 60 and it seems to struggle to just reach 60 mph. when normal for my truck is around 10 to 11 seconds. the truck is in no way missing or making any unwanted noises, it just wont go. it seems to do this most of the time but other times it acts normal. bought it cash from a second party seller so no warranty and taking it to a dealership is out of the question with what they would charge just to look at it. any help or suggestions is greatly appreciated.

 

I would start with a fuel filter.

 

fpdm next

 

Then cleaning your throttle body and maf .

 

I'm having the same exact issue. It will pull fine wot threw first but once I get to around 50-55 mph it will kind of hesitate and barely accelerates at wot but it doesn't feel like a misfire. Feels more like fuel or vacuum maybe? I got on it a few times yesterday to see if I could get any codes to pull up but nothing. And I changed the fuel filter 2-3 weeks ago and I just cleaned the throttle body and Maf last week. Spark plugs a possibility? I know I am overdue on those.

 

I checked the fpdm and it looked good and I will be replacing the fuel filter tomorrow n cleaning the throttle body as well n see how that goes. Thanks for the suggestions so far.

 

After my last post I went straight to Napa and got spark plugs, installed them, and problem is gone. Did a few hard 0-90mph pulls and she purred like a kitten the whole way.
(A very ferocious kitten)