I have a 91 F150 with a 5.0 EFI. I have sputter/misfire at crusing speed and, slightly at idle. It dosen't do it under load like when going up a hill. Here is what I HAVE replaced with NEW parts.
fuel pump front tank
fuel pressure regulator
ingnition module
pick up coil
distributor cap
wires
plugs "gapped .044"
rotor button
throttle position sensor
idle air control sensor
map sensor
egr vacum soleniod
air charge temp sensor
temp sending unit
vacum canister
timing chain set
o2 sensor
Here is what I HAVEN'T replaced.
egr valve "cleaned and works free like it should"
egr posit sensor
tad & tab soleniods
I'm at my wits end on this I don't know what else to do. I have it timed at 10 deg BTDC. Could a partially clogged cat cause this? This is getting to be a pain in my . Thanks for all help in advance.
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If it won't come off get the blue wrench.
08 STX Scab 4X4 4.6L 3.55grs S&b cai, 2.5" exaust with 18" dynomax bullets, hypertech programmer, 2" leveling kit
91 reg cab 4x4 5.0 EFI .030 over 3.55grs nls
84 reg cab 4x4 351W .030 over 3.73grs ls

 

did u notice if the distributer had play in it wile u were changing everything.

 

The distributor body is tight as far as internals go the shaft didn't have any backlash

 

Make sure the wires are run correctly and you are not getting crossfire. Best way to check is at night with no lights around.

 

could also be the pick up in the distributer

 

all new even seperated the 5&6 wires away from each other to prevent the notorious misfire that many people have told me about

 

what about the fuel filter and cleaning the injectors in chem dip and rebuldint them with new nossels filters and orings i had a shutter in acceleration and i rebuilt my injectors and it took care of the problem

rebuild kit has like $20 but make sure u get the one with the little filters to take the old filters out i believe i used a number 10 machineist screw and the chem sip u can get at any parts store i think i payed $20 for that also

 

New filter haven't done any thing to the injectors sounds like a plan

 

Before you pull the injectors, you could try running a couple bottles of Techron through the gas. If it makes a difference, then you know it's the injectors.

 

that stuff never worked for me but its worth a shot especialy if u dont have to pull the plentem but if so it cheap and easy to do the longest part is waiting for them to be dun.

i took my injectors out at night and dissasembled them and dropped em in the chem dip then in the morning i came out blew them out with the air hose and rebuilt them and put them back in. make sure if u do it dontpinch or roll an o-ring or else ull have a leak

 

I ran so much seafoam throught this thing it aint funny. I hate to pull the plenum especially after all the gaskets have been replaced. It dont sound like a hard job just hate doing that kind of work out in the driveway. Oh well if something goes wrong I have 2 other sets of injectors.

 

then clean n rebuild one of your set and swap them in. i do my stuff in my driveway/onecar garage i dont like taking my vehicals to someone else to fix.

 

also i know alot of people woulnt like this but i dont depressurized my fuel rail i drape a towle over them and use the pressure in the lines to help get them out but if u do dont forget the towle orelse gas will be everyware

 

In the words of a good friend of mine "seafoam is over used crap!!" Seafoam contains IPA, isopropyl alcohol, and that stuff is detrimental to rubber and plastic parts. Also with the miss being at cruising speeds I would suggest pulling the plugs and inspect them for cracks in the porcelain. It's very easy to damage a plug during installation. Plus there's a chance one of them may have been bad out of the box. Same with anything else you might have installed.