I’ve got a 2008 5.4L, starts well, idles well, drives down the road great! But once she is warm, and maneuvering the truck in the 900-1500 rpm range in either fwd or rev my VCT2 goes to 50* and I get she starts to stumble and clack. No codes what so ever. Engine was replaced about 6-7000 km ago. Checked timing, tensioners and guides. Oil pressure is well above the 15th psi min. Anyone have any insight or experienced this before?

 

Were the vcts replaced. I would do an engine flush then maybe new vcts . Are the phasers oem . . take valve covers off and inspect phasers.

 

valve covers and timing cover were just off. Ran like this from day 1. VCT solenoids(OEM) tensioners(OEM), chains(OEM) all replaced by me. Only thing left I feel is phasers. Of which you can not inspect internally unless removed. Either a new VCT is sticking (unlikely as I’ve swapped side for side and the problem did not follow or that bank is seeing something within parameter to make it advance, or the phaser on that bank is not retarding itself. 🤷‍♂️

 

You can look down at phaser to see if its distorted,front plate should be parallel to rear . When at rest the middle finger of the three should be inline with the L. You can use the wedge method by carefully marking links to change it out from the top . Non oem phasers are junk, all of them .
Oem phasers are expensive so don't be surprised if you have the non .
I don't like the wedge method but in some cases its viable.
Watch ford tech malukoco he is the expert .
You must keep engine internals very clean , this engine uses dirty oil to hydraulically control cams by using pulses from pcm to rapidly release oil pulses from vcts to phasers . It has small oil passages and a weak factory oil pump . Carbon from combustion does not care if its high mileage oil it still gets dirty .
Using oil this way calls for more oil filtering than was called for from ford , It needs the hv340 oil pump from melling to maintain oil pressure and flow . Some remans upgrade the oil passages and use better rollers with smaller oil holes . The plastic tensioners have a habit of loosing their seals . You can install the older ratcheting steel ones that have no seal .

 

Hopefully you don't have high mechanical resistance on the cam on that side. But the only way you could check it during timing is with all the followers out and being able to spin it by hand . That's a lot of trouble going back to pulling timing cover .
I'm surprised you are having this problem this soon on a reman . I have briefly talked to some machine shops about line boring heads for cam bearings, I haven't had any local shop get me anything i could rely on .
You could look at oil flow into the valve train while you have it open but it will be messy .
I know there is a debate about how many pounds of oil pressure is okay to drive phasers . . I'm curious as why you would have to change vcts,timing chain , tensioners this quickly on a reman , who did this reman . A true good reman would have upgraded many parts - a local shop may not .
Odds are its your phasers , oil pressure is measured where , you did not say what bank you suspect . I believe i would drop that oil pan and look at oil pick up and o ring ,you never know when a plastic seal on an oil bottle got in there.
A bad phaser is not fixable - need new one inspect before you put it on .Check out the holes in the end of cam where the phaser mounts .
Check out torque on cam journals, 89 inch pounds in sequence. You may have to check out wear on each one . Only you know what was done to this engine and who did it -warranty ?