2004. Why did it lose acceleration?

if you have it in neutral then the car will not accelerate
just the engine will increase in rpms
if it is a manual and in gear and you increase engine rpm but the car is not moving, it is more that likely a clutch master cylinder or cable problem
if automatic , run the fault codes and check for a problem torque converter clutch servo/solenoid problem

Transmission slipping into neutral. - Ford Truck Enthusiasts Forums

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Mar 29, 2009 - 2004 - 2008 F150 2004, 2005, 2006, 2007 and 2008 Ford F150's with 5.4 V8, 4.6 V8 or 4.2 V6 engine ... into happening using a combination of the gas and overdrive switch. ... Sorry for the long complicated post, but it's driving me crazy. ... i know that i can get my tranny to rev up up like its in neutral while in ... really useful writeup on dreaded e4od i found
Nov 22, 2009
Tranny ?'s= while driving engine free revs like in neutral
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Blinking 4wd lights? READ THIS FIRST before going to dealer ...
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what makes you thing the tires/wheels tighten (felt by hand off ground?)
my guess , you meant it seems. like???
1: lost engine power?
2: transmission not up shifting?

is this a auto A/T or manual M/T tranny,
if A/T , you need to look at the engine RPM when you lose
power (acceleration on demand)

RPM rises, car dont move faster ,this is tranny slip.
RPM fails to increase, and speed, up hills. this is called lost engine power.
lost engine power can be caused by , bad spark (tuneups skipped?)
or weak fueling.
weak fueling too can be cause by skipping the fuel filter step in the tune up list.

the best thing to do is to take it to a mechanic. the transmition is slipping

You should get it to a trany shop right away. It most likely a simple fix, if you continue to drive it like that you are going to wreck something.

Do make sure there is plenty of good tranny fluid and filter in the system, If the tranny doesn't catch right try disconnectning the battery for 15 minutes and plug back in, It should reset the computer which will hoepfully fix the problem without having to get tranny rebuilt.

change fuel filter and drain water seperator

if oil level ok ?? then cost of repair is more than the value of the car

Hello;
Are you getting the check engine light? If so the electronics may have gone out. You may not need a rebuild but you won't know till you pull the oil pan on the transmission and inspect the contents. You may also have lost the neutral safety switch. It is mounted on the drivers side of the transmission. Check those out first and let me know what codes you get.
For Ponchoboy; the clunking and hissing you hear are teminal root causes. Drop the oil pan and if it has a lot of filings and metal it is time for a rebuild.
Hope this helps; Rate me highly;
Rich
RPM Northwest

try running some fuel injector cleaner through the system. i have a 95 century and i have a similar problem but cleaner helps :)