I want in on this one too. I have an 02 with 182k miles, and mine has just started doing the same thing. You pull out and its good all the way up to about 2500rpms but after that its just struggling to get out of its own way.
I keeping thinking its tranny related, but maybe mine is CAT's for fuel flow too. When getting on the interstate you can apply approx 50% throttle and two things happens first its like the truck shuts off a few cylinders and at the same time the truck doesnt downshift, the only way I can get it to downshift and seem to have any power is to floor the thing. and even then it just feels sad.
I had a couple of codes P0455, and P0457. Not sure how these would relate to our issue.

 

Oh crap I just found my problem I think I just replaced the intake manifold and we ran the vacumm lines for the evap system, and the one that plugs into the top of the fuel regulator to close to the EGR valve, they are melted in two pieces.
I take it the vacuum leak isnt helping,. and I bet my fuel pressure is off due to the vacuum on the fuel pressure regulator being non existent.

 

It took a few weeks to get a set of catalytic converters, but that fixed the problem we have had with our 2003. I was a little concerned when I took out the old cats there was no rattling of broken ceramic. The only ceramic I could see thru the pipes looked fine. One of the ceramics must be melted or clogged. The oxygen sensor connector on the right side forward is a bit difficult to get to. I could get to the connector after dropping the pipe and spliced in 2 ft of wire with a second connector I can get to if that sensor ever goes bad. After installing the new cats the idle is very smooth, off-line acceleration is better, it pulls great uphill thru 4000 rpm and no SES codes.

 

I have a 2005 Expedition 5.4 95000 miles and am having similar problems, except mine began with a strange tick/tap noise. I recently had the TSB performed on the truck have the cam phasers, all the lash adjusters, VCT's and the spark plugs changed out, since everything was taken apart. Shortly after this happened the trans went out, in which I had that rebuilt with a shift kit.

The truck ran great with no sound or problems, although since I have had it it seems to shake at idle, some say motor mounts, its annoying, but it is not the RPM's.

Well here is the issue, as I said it started making this metal like tap/tick sound. It sounds like it is coming in cylinder 3 or 4 and at where head meets block at cam speed. It sounds horrible, but the mechanic told me it is normal. I had 2 other shops inspect who cannot determine exactly where the sound is coming from, but they say the noise is at cam speed. I also had my tranny guy inspect it as well as a muffler shop (no exhaust leak).

Now about 2 days ago the car started this same issue with acceleration. It drives perfect, starts, etc. there is no misfire or engine codes. It does not hesitate, not sputter, but at around 3000 RPM under load, (floored) the car makes noise but doesn't do get any faster. however, if I accelerate very slowly it will get faster. I am tapped out and don't know what to do.

I have small children and don't want the wife and kids stranded in this heat because I am told this is a normal characteristic of the 5.4.

Any help appreciated and thanks in advance

 

Our 2003 5.4 had a shake at idle for quite awhile before the springs in 2 spark plug boots got rusty enough to set a misfire code. The shake was very random and sometimes gone for a few minutes. It would get worse when it rained. There was water in the boots from a leak above cylinder 6 & 7. Replaced the 6 & 7 COPs after it finally set a code and the shake was gone. The idle RPMs did not change.

We also had a metal ticking noise for quite awhile and is now gone after replacing the cats/y-pipe. At first it sounded like it was coming from near cylinder 4 and I thought maybe a sticking starter was nicking the ring gear. I used one of the stethoscopes from Harbor Freight ($3.99) and it is amazing how well it works. Determined there was something inside the outlet of the right precat flapping in the exhaust flow and hitting the casing. Had both my sons crawl under and we all came to the same spot in the exhaust pipe where the sound was coming from. At higher speeds you either couldn't hear it over all the other noise or the flapping rate changed.

The lack of acceleration above 3k RPM sounds just like what was happening with ours. Car ran great and would get to 75 if you kept the RPM below 3k, but try to accelerate hard or pull a hill, forget it, no strange noises or hesitation, just no more power. Over a few months the lack of power kept dropping in RPM to 2500. Check the fuel pressure at speed and if it's low try changing the fuel filter before blaming the pump. Check the vacuum at speed. (I duct taped the gauges to the wiper.) On ours the vacuum would drop to 2-5 inches at 3k RPM when increasing speed slowly, not floored. I found a website reference that stated the low vacuum reading under these conditions indicated a clogged exhaust. After changing the cats/y-pipe (Eastern) the vacuum cruising at 2600 RPM/66 MPH with O/D off is 15-18 inches and the car runs great.

 

Thanks for the quick reply and update on the issue. I will look into the COP's as well as the CAT's. This thing is driving me nuts!! I just dont have the money to keep throwing at this thing, but I definitely cant afford a new vehicle when overall I love this one.

I am hoping the CAT/COP issue will resolve the acceleration and ticking rattling sound.

As for the the shake, my idle also maintains position without altering a solid 650 or so, whatever standard idle is, but annoying as heck when you are at a stop light and you feel this shake in the car...

I will let you know what I find, if anything regarding anything. I may just throw a complete exhaust system on since I can get that probably cheaper than paying for new cats.

 

Have 03 Expy 5l Eddie Bower and had no acceleration at speed. Just had Cats replace and running much better. Now though the Mechanic found Yellow inside the pipes. Anyone have a clue on this?

 

My 03 5.4L is sluggish under hard accel because i have a stretched throttle cable. But it seems like a bish to change since i got adjustable pedals.

 

Some say that's a result of anti-freeze in the exhaust in which case you might have a blown head gasket. Others say it's a result of exhaust gasses being hotter than normal. Unfortunately that can be caused by a rich or lean condition. A rich condition adds extra fuel into the exhaust where it burns and generates the extra heat. A lean condition is just a naturally hotter burning mixture. However, in either case it seems to be caused by an improper fuel mixture.