Hey All,
New here and had to post as I’m having some issues i cannot figure out.

I recently bought a 99 f250 with the 6.8

i got a screaming deal on the truck as it has been sitting for 3 years.

it’s got a ton of modifications done and will be a solid truck when i get it running properly.

when i bought it, it wouldn’t run, i put a fuel pump in it and it fired right away. But now I’ve been chasing idling issues, and the p1742 code from the trans.

i changed the MAF sensors and after some research found the cylinders 1 and 9 weren’t getting any fuel from the injectors. So i put two new injectors in and the truck is idling much better.
the problem is now,

the truck runs perfectly when in park,

but as soon as i go to drive it, it wants to fall on its face.

On flat ground or no load it will run okay, but the moment there is a slight incline or a load on the truck, it start almost sputtering and really doesn’t run well until higher rpm’s (2500 or so) then it’ll start to run good.

the transmission is acting weird, where it won’t shift unless i let off the throttle, then it bangs hard in gear.
it down shifts sometimes but other times it almost seems like it starting in second gear.

I thought maybe the code and the truck running like **** were related but i think I’m still having issues. I’ve replaced plugs, MAF, checked for vacuum leaks, new fuel pump, checked fuel pressure, and changed the trans solenoid when i did a tranny flush today.

any input would be awesome. Thanks !

 

check all your vacuum lines , i had to do that with mine itsa 99 also. your transmission should be the 4r100 4 speed check your shift solenoids and filter as well as tranny fluid may be burnt and need a good flush.