I have a 97 F150, 5.4L, since I got the truck a couple of months ago I have noticed, what I call a stumble during acceleration, occasionally. I first tried fuel injection cleaner, that didn't help. Next, I tried premium gas and it helped alot. Everytime I try to put regular unleaded in my tank I get the same problem. I have 77000 miles on the truck and don't know when the last tune up was, but before sinking alot of money into tuneup items I wanted to see if this is a normal thing for these engines or not. I know premium is not that much more expensive than regular, but it does add up, plus is premium really that much better. Other than when I use the regular unleaded there doesn't seem to be any mechanical problems. I just find it hard to believe that I need to run a higher octane gas to make my truck run good and that there is not something mechanically wrong somewhere.

 

That should not be happening at all. There is no way around maint., unfortunately. You may have picked up some deposits in your engine. This will call for higher octane demand...etc.
Before the tune up you could try some techron additive or Redline SR-1 Fuel system cleaner.

good luck.

 

You should check all of your spark plugs and spark plug wires. I had the same problem, when i would accelerate it would "stumble". But, it actually turned out to be an engine miss in cylinder #8, at least i believe it was that one, it was the far back one on the passenger side. For awhile it wasnt bad, but then it got to be a hassle jus to drive, it had very very poor acceleration. Then my check engine light came on, and ford told me it was my mass flow air sensor, and to me it kind of made sense. When i got it back from the shop it still had the problem. A couple of weeks later the check engine light came back on and they told me it was a missfire in that one cylinder. I took it home and looked at the wire and and it seemed to be fine, but after i put it back on it ran better than when i first bought the truck, But the problem came back so i just replaced the wires and now it runs perfect. Oh yea, i used to do the same thing, run premium gas and it did help. But not as much as new wires did.