Hey guys and girls, 05 Fx4 5.4 59,000 miles- Stock. have owned the truck for about 10,000 miles. runs great but ever sence i bought the truck when i give it wide open thottle for passing ect it kicks down like normal but 4000 rpms + it gets sluggish almost like its missing, but its really not missing i checked it when it was parked motor is not shaking ect, also gave it some pressure under a load ( trying to do a brake stand but not letting the tires break loose) and it doesnt miss! only when its wide open and goes to kick down it feels like its lugging then when it goes to pull not everytime but alot. seems to do it mostly when its cold out. really bugs me! i could see if its missing under a power stand or something id say put some new plugs or a tune up but it only does it when i described b4... pls help! any idea's?? ohh yeah 1 other thing when it does do the lugging it doesnt get all the way to the normal 5,000 rpms and shifts it seems to shift at 4 1/2 when its doing its bad thing it does

 

When is the last time you changed the fuel filter?

 

X 2

 

Yes, the fuel filter should always be the first thing to change.

 

My truck does the samething even with a new fuel filter.

It's my IMRC (Intake Manifold Runner Control) that doesn't work. Been in the shop for that, cost me 700$ 1 year ago, but never when over 4000rpm in the past year or almost.

Notice 1 or 2 month ago that the truck was still doing it, so i will look at it again.

 

I've noticed my 05 lariat 5.4 is sluggish compared to my brother's 07 kingranch 5.4...When I say sluggish, I'm referring to the throttle response and acceleration. The '07 seems alot "peppier". I'm not sure if its because they tweaked the engine different or what but the difference is definitely there.

 

I have heard Ford has updated the PCM in the later models I think 06 and up I believe...

 

07-08s have different programs and 8-10 more hp