Ok so I solved the mystery 5.4 3v issue. This was on of the toughest ones I have had in a while. Turns out there where multiple issues. After running every freakin test and checking everything I could rule out through electronic means I decided to tear the front cover and intake off the motor and verify that everything was in time and there was nothing funky going on inside. Well everything under the front cover checked out but under the intake is where it got interesting. Who ever installed the new engine did not clock one of the knock sensors in the right direction. So when the intake was installed it pinched the wiring going into the sensor which caused a intermittant bad connection, the other knock sensor was installed with to long a bolt and would not tighten down enough to fully clamp it to the block. The incorrectly clocked sensor also pushed up on the bottum of the plastic intake enough that over time it caused the intake to twist and prevent a intake runner valve on bank two from moving freely. The lack of a correct signal from the knock sensors caused the variable cam timing system to malfunction under certian driving conditions and throttle settings. Some times it would advance or retard the cams correctly and other times it would not. Truck runs great now after correcting the issues.Hmm indeed. In addition to mine I work on a fleet that still has probably a dozen. Update when it's solved.
Last edited: