having a major problem... No power when it gets warm.. Replaced MAP, TBS, plugs, wires, cap, rotor, fuel filter.. has dual tanks and has same problem with both so im leaning away from fuel pressure. After it gets warm and you give it gas it almost seems like your letting off the pedal.. If you "feather" the throttle it has power... Im totally stumped!!!

 

any codes present?

it maybe the CATs showing signs of meeting their life expectancy?
it also could be a sign of a very tired engine?
vacuum leaks are also something to look for.

cap and rotor on a 97'??

 

What motor do you have?

 

5.8 gas. Old body style.

 

Look at the base timing with a light then how much advance tendency there is when you jazz the throttle.
For base timing pull the TFI harness series plug so the EEC can't affect the base timing, should be close to 10° advanced.
When you put the plug in on a cold motor you should see about 20 to 24 ° until the motor warms up.
What is the intake vacuum level? Should be around 20 inches.
Just have to look at all these items until you see something out of line.
Intake air temp sensor might be causing part of it.
Coolant temp has a lot to do with power. There are two, one for the gage and one for the EEC.
On the cats, you could weld a nut on the head pipe and a 1/16" hole, capable of accepting a fitting for a 1/8" line to use a Vacuum pressure gage that will read a few pounds pressure by the needle moving below zero. Rev the motor to 3000 and look at the back pressure.
I should be no more then about 2 psi.
Good luck.

 

there are no cats on this truck, straight pipe to muffler.. cat was getting hot as hell and thought that it was causing the issue.. (thought it was plugged)

 

Getting 'hot as hell' dosen't tell anything.
They are supposed to run hot at over 600° in order to clean the gas of 3 emissions by products.
And now you say there are no cats!
What else did you leave out?

 

No cats will not make it run the way it is.. Im on here b/c I know basically nothing about ford crap, this is my boss's truck btw.. And the cat was starting to glow red at the intake side of it.. so that was the first thing to go.. then I read up online about these pieces of crap and found that guys having similar problems replaced the MAP sensors and it fixed it. so that was worth a try.. My boss and I are both about ready to go trade it off on a nice duramax and be done with these problems..

 

BUT.. If someone on here knows something about this type of problem plz let me know.. Im not asking for a lecture on how things work or that there are no cats..

 

we are trying to help...& understand your frustrated but the info that your providing isn't matching up with the correct year. & your first post did not indicate the lack of cats...so we end up covering old ground from your prospective.

Please clarify...what year do you have and size of engine. Is it a 96' instead of 97' ?? there are differences in body style and engine options. 96' would had a 5.8 V8 as a option and 97' would have had 4.6 or 5.4, these are very different engines.

but the info in ^^post #5 above^^ is a good start...vacuum leaks are killers for performance no matter what engine style or make you have.

was this a sudden onset of lack of performance in the fully up to operation temp?

I'd lean towards a compression check...to gauge the health of your engine...both cold and warm engine

 

yes.. its a 97, old body style f250... door says 1/97 and the title says 97.. and its the 5.8.. the problem seems to get worse the warmer the motor gets.. but like I stated it can be compensated by pulsating the gas when trying to gain speed either at full throttle or half throttle etc.Almost like your making up for a bad carb (which I know it does not have..lol).. truck only has maybe 140k on it and has always been maintained well.. and this problem was first noticed this spring when I started working where I am now..

 

I realize you mentioned you have good fuel pressure...but also dual tanks?

when this acts up....can you hear gas gurgling in the tank that isn't being used. Wondering what kind of fuel pressure you have when this is acting up ?

 

Ill check it some time this week but I dont think there is any gurgling in the other tank.. think maybe some bypass is bad?

 

how many miles on the engine ? and have any of the injectors been replaced ? if lots of miles i would check the compression , and then do a leak down test on each cylinder to see what the inside is doing ! dont lean away from the fuel pressure it can tell you a hole lot of info also , only takes a few minutes to check !