ok guys im pulling my hair out with this truck now

1997 f250 7.3 auto 4x4 crew cab with 282k

ok so before we begin im sorry for the long thread but i feel its necessary for my issue. ive done a lot of research and a lot of testing to no avail, ok here we go.

i recently bought this truck with a bad engine for a pretty good deal,

• when i bought it it had pretty bad blow by

• engine felt very underpowered

• loads of bluish white smoke

• did a contribution test and cylinder 1 was the issue and occasionally cylinder 3

• i also pulled a p0476 exhaust back pressure code whuch didnt set the cel but was still in there

heres what ive done in the course of a month

i decided i didnt want to rebuild the engine because i didnt want the truck down for too long, so i found a good used engine with 143k and no blow by.

• truck still feels under powered

• pours white smoke only out now but no blow by

• failed a cylinder contribution test on number 3 cylinder (i have swapped a know goiod injector for cyl 3 with new o rings)
• i have checked the whole harness and it is good, i did both a continuity test on everything and took ohm readings according to specs and everything passed
• new fuel filter
• i have replaced idm with a 120v one tiny bit of difference but still nothing

• at 3rd and 4th gear the truck shakes like it cant pull anymore(did it very bad with old engine and not too bad with this engine but still noticeable)

i have a snap on code diagnostic computer that is able to do quite a bit

i have done a buzz test and all sounded the same and also passed according to the reader

p0476 code is still [resent, i have watched the exhaust valve while doing a KOER test and valve fully operates open to close, i have also cleaned the back pressure tube and sensor which was pretty dirty with soot, doing that made the truck feel a little more peppy but still under powered

any insight would be extremely appreciated i am pulling my hair out with this thing now.

i suspect the ecu because its the only thing that remained the same constant when i replaced the engine and still had same sort of issue what do you guys think? thank you!!


there are thing that im forgetting that ill add as i rememeber

 

Did the replacement engine come with the wiring harness, or was the original truck harness used? If the original one was used, have the valve cover pigtails been changed? If the pigtail to the 1 & 3 injector has been changed, maybe the PO has miss wired the leads to injectors 1&3, which would lead to the injectors firing in the wrong order. My other WAG would be the ECU, as you stated.

 

Can make sure it is wired correctly with the help of this.
remove IDM connecter and ohm it all out

 

how much has it been run since the injector was changed? you could still have oil in the exhaust system burning out (white smoke)
air in high pressure oil system (rough running)
has this truck sat for years? (bad fuel)
pinched wire under valve cover, seen it before makes them run real bad, same with an internal harness not plugged in all the way.

 

you sir are a genius!! That was it!!! Man I'm so relieved, you guys don't know how long I've been messing with this thing... and the messed up part about it is that I took apart the harness and the injector plugs were crimped and occur them and soldered each one, one by one making sure I didn't lose their place lol

thank you!!!

 

Oh yeah that also can make a huge cloud when you tow first time and EGTs burns out the oil in the exhaust from doing orings, I got nervous at first on my first trip but it stopped soon after the second time I hit 1200 degrees.

 

I've driven the truck about 400 miles with it like that so I doubt it's still in the exhaust, I did think that for a while but it never cleared out however it did change colors from unburnt fuel and oil in the exhaust to now just straight in burnt fuel so I'm gonna re solder the wires in the morning and give her hell!! I'm still prolly gonna see smoke just cos residual but it should all be well