i got a 88 f-150 with a 90 351w efi. well the swap went fine. i have had the motor in for just a little over a year now and i am happy with it for the most part. i will start at the begining. when i had the 300 six in the truck it ran great until it got warm and you let it sit and idle and the truck would kill itself, and have to sit for a little while before you could start it again and smell like it was flooded. well i just changed the motor and the first time i cranked it up it started great right that is what i thought also. well after that i put all kinds of new parts into it.
tps
icm
distributor cap rotor button
plugs plug wires
fuel relay
computer relay
fuel pressure reg
new coil
well after all that the truck runs good when you get going but while taking off and sometimes after you let off the gas it hesitates like it's just bogged down then all the sudden it takes off runs like new and does until you let off the gas and it does it again most of the time. well this has me stumped i have thrown parts at it trying to fix it and i am at the end of my rope . i had plans on getting my new bed and door, hood on it and painting it this summer but i will not do that unless i get this fixed. and i still need to pull codes but i really want to see what you guys thing about this. i was maybe thinking crossfire? because i do not have my plug wires placed right but idk anymore. thanks for the help with this guys

 

come on someone must have some info on this for me

 

what's your fuel pressure reading? Does the fuel pressure bleed down? single or duel tanks? did the engine run fine in the previous truck? Check the EGR to make sure it's not sticking open. How about timing.

 

well the other motor die while idling but other than that ran good. and i put a new fuel pressure regulator on just two weeks ago when i tested the pressure it was within limits but on the low side of them all and just single tanks on this truck also
when i tested the pressure on this motor the 5.8 after the fuel test it kinda went down fast also if that helps
also i got the timing at 11 btdc and well the egr kinda is useless i unhooked all the smog stuff and just plugged the egr in but with true dual on i would think it would just go out the back no cat either

 

fuel pressure with vacuum hooked to the regulator should be 36-40 and pressure with vacuum line unhooked should be 39-42 or so. not advising this (but i do it all the time because ive ruined my fair share of them) but if the base fuel pressure isnt high enough, and you know your filter and pump are new/good, you can crush the regulator using a vise and a 1/4 drive socket that fits over the vacuum nipple. just squash it a tiny TINY bit. Ive had some pretty crappy new regulators before and they have needed a tweaking.
does your truck have the diaphram in the fuel pressure line feeding the engine. Ive swapped a 351 into a 6cyl truck before and that diaphram was bad or 6cyl specific and made the truck run weird. I put the v8 line on the truck and it ran mint.

The 6cyl not starting when it was hot, was more then likely the ignition module on the side of the distributor. Thats why they remote mounted it on later trucks and cars. They get hot and fail so truck stalls, and then when cool it will run again. is that what you are refering to when you listed ICM
Clean your idle air valve, it may be sticking closed and bogging the engine when you fully lift off throttle.

 

the new icm is on the 5.8 motor i swapped in and for the fuel line having a diaphram i don't think so but i will look where would it be ? and it does have a new fuel filter on it also

 

i would test the tps and did you check the fuel pressure under hard acceleration. wait did you swap computer and harness or carb it ???

 

i swapped in the computer from a 5.8 and i was thinking of going carb if i didn't get this all worked out to be honest . and the tps is good i checked it before i put a icm and new distrubutor on it

 

well i took the idle air vavle off and it wasn't setting all the way even after i cleaned it guess jus wore out well i am goign to put a new one and and see how it goes i let ya know thanks for the ideas guys keep them coming