Hello everyone
and thanks in advance.

I have a 2005 f-350 with the 5.4l Triton V8 the problem I am having is that when the truck is cold it runs perfect but when it reaches operating temp it looses power.

what i have done so far:
replaced all 8 spark plugs, cleaned MAF sensor (with proper sensor cleaner),
checked for vacuum leaks, replaced fuel pump and filters, and checked all wiring.

I am now at a loss as to what the problem could be

 

When you say looses power , just what is happening? Be as specific as you can.

 

What I mean by looses power is that when it reaches operating temperature and you give it some throttle to go up a hill it is very under powered . its like it is running on 4 or 6 cylinders

 

Did you have this problem before you changed the plugs?
When the engine is warmed up and idling can you feel any popping at the outlet of the exhaust ? Does it feel like it is missing on one or more cylinders? If the answer is yes to these questions there is a good possibility there is a defective coil problem.

 

when engine is warmed up there is no popping . how it started was got the truck from a friend and it had no power at all cold or warm. i replaced the fuel filter which was clogged solid, then replaced fuel pump and screens put in fresh gas then it ran awesome fore about 4 days. then i replaced the plugs because it was running bad when warm, checked plugs and coils all checked fine, cleaned MAF and still no change. it runs like a brnd new engine when cold but runs like CRAP when warm. It does have an exhaust leak and ithink maybe my cats are plugged possibly

 

What I have found when I came across plugged converters the engine would idle fine, but just couldn't get it up to high RPM , even in park. Would think if cats were plugged in this case it would run crappy when cold also. The exhaust leak could be influencing the fuel control depending on where the leak is located before or after the last o2 sensor.

 

Thanks for all your replies Hanky
disassembled the cats and fixed the exhaust leak to no avail. cats where plugged solid and on one side it was plugged so bad that the pressure actually broke the welds on the cat that's where the leak was coming from, the thing is running so bad now cold or hot doesn't matter going up a hill full throttle was doing 2 miles an hour not even joking.

and now it sounds like my cam phazers are done in now too, I think it is time to get rid of the truck and buy a dodge lol

dont know what else it could be and thanks for all your help