All, I have put 2500 miles on my '05 Lariat Screw 4x4 now and have noticed that the acceleration is not linear! Consistently when I hit WOT the engine will rev normally until about 3/4's of the usable powerband - then the rate of acceleration seems to drop off by (educated guess) 25% until it shifts. I have been experimenting with the WOT and have noticed that if I lift - just a hair- when it starts to drop off it will actually accelerate faster.....this must be the ECU/throttle control systems limiting the rev rate?

For those of you with the aftermarket tuner - did it cure this characteristic? If so - the tuner would be well worth the price....

I'm still noticing the 1st to 2nd shift "drop off" as well. When I'm at about 3/4 of WOT and hit the shift to 2nd - the RPMs seem to just drop off and the engine is sluggish - is this another "trait" of the ECU/Throttle control systems design by Ford and "curable" with the addition of a tuner?

So far I'd have to sum up the 5.4's performance as this: "For a 300HP engine it doesn't seem "spunky" at all - rather it feels very lazy.....even if it is in a heavy truck - it seems as if it should be working harder, revving faster, etc. Is this engine so different from my 4.6L 3V in my '05 GT that revs like a banshie and seems to "leap" when I get on it??? I realize the GT is much lighter, etc., but still the 5.4 doesn't feel in the least bit lively.....


Sorry for the long post - but I'm trying to understand/learn about this 5.4 3V engine and it's characteristics - is this engine weaker than the 4.6 3V in my GT (thus revving slower, etc.) or is it simply tuned different because it's in a truck?

 

its the tq converter playing

 

I've noticed the same problem with my 2005 Expy. It's the electronic throttle control and computer trying to out smart itself.

My dealer told me they have installed a couple of Superchips programmers and this has fixed the problem by allowing the throttle body to open at full throttle at lower rpms Said it made all the difference.

Unfortunatly, Superchips has no programming available for the Expy yet. Only the F150.

 

im having the exact same problem. I can def. feel the 300 hp sometimes, but its very inconsistant. having a reg cab helps i suppose. im thinking a dealer reflash of the ecu would fix it? hopefully someone who has had this problem and had it solved will answer. i would like to get a tuner, but im saving for a supercharger and dont want to waste $400. i would like it to run better in the mean time though...

 

I had the reflash done, made a great difference in mine. Much more responsive, especially on the low end.