Just an update to the status of my truck.
When I replaced the fuel filter, the engine improved to about 80% from how it performed prior to the symptoms appearing. When I put the fuel injectors back in after getting them refurbed, I hoped that the engine would be back to 100% but this was not the case. The problems actually seemed to be a little worse immediately following their install.
Here's the strange part.
Recently, the symptoms have suddenly begun to decrease. During the injector removal process I disconnected the battery, clearing the ECU trim tables. During the relearning process, there was no change in the symptoms. I've put well over 2k miles on my truck since reinstalling the injectors and only now am I getting improvements.
My truck performs at about 90% from what it was before the symptoms started. The sound of the exhaust is still louder than before and my truck still shakes while driving at highway speeds due to the engine vibration. The engine still shakes a little when revved in neutral, just at different RPMs from before. Previously the engine vibration peaked at 2000 rpm. After the injectors were refurbed, the vibes peak at 1700 and 2300 RPMs. The torque is good but I think it should be better.
I bought a fuel pressure gauge to check the fuel pump but nothing conclusive came of that. I got 45psi while idling in Park. With the gauge connected I did I test drive and the pressure only dropped to about 42 psi when I accelerated to 50mph. The gauge dial indicator shook rapidly ± 2 psi while centered at 42 psi during hard acceleration but was perfectly still while idling. Don't know what this indicates if anything.
I'm still confident that the main problem is the air/fuel mixture and I suspect a lean condition. The sound of my exhaust and the engine suggest that one cylinder is combusting differently from the others.
RECAP
With the exception of the slight pinging, the symptoms appeared overnight and are now starting to decrease for no apparent reason. If I could determine what would act like this it would help me find the problem. At this point I don't know.
I'm going to swap the injectors (left rail with right rail) without disconnecting the battery to see if there are any changes. If so, this would indicate an injector issue. Another reason I'm going to do this is that when I reinstalled them, I put them back to maximize their balance (as measured by the injector refurb shop) with the engine firing order. The problem is that I used the diagram in the
Haynes manual which
has the banks reversed for the V8. Don't know why I hadn't noticed this before. The V6 diagram is correct. I doubt that the injector balance is an issue but the swap is a good test at this point.
I might try swapping the coil packs before doing the injectors, since that would be very easy. I really don't think the coil packs are an issue but I could cross them off the list of possibles.
I'll post any updates.
Paul