ok here is the deal, just did my 4.6-5.4 swap a few weeks ago (on a 2001 4x4). I got it all swaped it started and ran pretty well (for using the 4.6 harness and computer) i mean yea it was sluggish, but you could still drive it.. I had set up a appointment to get it tuned so i was happy. Well a few days before i was suppost to get it tuned i drove my truck over my brothers house (ran fine on the way over there) and then when i decided to leave it started and idled fine but as soon as you would give it gas an try to move it would fall on its face seemed like it was almost missing on every cylinder.. Bad enough where you could not even drive it anymore.. So i'm completely stumped? any ideas?

 

ok so you do still have a cop ignition system right? was the cel on at any time? its most likely the tune. but it could be a very dirty maf, or possibly a clogged up cat now, or possibly low fuel pressure.

 

yes still have the cop ignition, i dont know what the CEL is , cleaned the maf, i have no cats

 

CEL= Check Engine Light.

No cats could be your problem. When did you remove them?

 

i made my full exhaust at the time of the swap, also my overdrive light on the shifter is blinking ( also all of this happen all of the sudden)

 

If the overdrive light is blinking, you need to go to a shop that has a code scanner that can read Ford transmission codes. The cheapos that Autozone uses can't read them.

 

Absolutely... The truck will run on the stock 4six tune, just not as good as it could. When you remove the cats, you'll flow more than your tuned for (Some call it "Backpressure"). So that added to a 5four running from a 4six PCM - She can't fix herself when the program doesn't exist yet. She doesn't know what to do.

How could anyone do a motor swap and not know what a CEL is ? - Among other things mentioned ?

Anyway, I'm not saying that's the whole problem here, I don't know what all you have done incorrectly (if that's the case) but, it sure didn't help things.
I tried running cat-less once out of curiosity- The engine ran, but was missing enough torque/power to notice right away. That's simply because we are not tuned to run without.

You can run with one cat per side, but not without all 4 governed via stock tuning.

 

my question is what did you do with the 02 sensors???

and no backpressure equals bent exhuast valves in the long run. . .

 

the thing is tho, it ran pretty well for about the first week after i did the swap, then out of the blue one day it started running like ****?

 

cause it relearned, and with the absense of fuel/air ratio and knowing what its buring and not burning and ho wmuch air to add and how much fuel to add, it shat out... who cares why it happened. 2 cats, re-install 02 sensors and have it tuned.

end thread

 

Mann, sounds like a bunch of problems to me.. No O2's ? How would you tune it ?? lol

Yea, It's probably just burnt now.

 

how bout it brew. . .

do your homework before getting yourself into a EFI mess such as this... EFI only works is the computer knows what coming in (MAF) and whats going out(02's)

 

Not sure what you mean. Mine runs, his don't.

 

 

the top two 02's are in the bottom two are not i need to get bungs and weld them in... why do i need cats?