I've posted a couple of times about a lean running 5.4. I've got a bunch more information so I'm starting a new thread keying on the problem.
When I start the truck, the Short Trim on both banks behaves reasonably. Mild variation from about -2% to +2%. The Long Trim immediately goes to +25%. Revving the engine to about 1,700RPM reduces the LT to about 12%, but it immediately shoots back up to 25%.
After a few minutes, both banks throw lean codes and the Check Engine light comes on.
This started more than a year ago when the O2 sensor on the right bank failed. The sensor was replaced and all was normal for a couple of months. Then the lean codes started showing up.
I've replaced the fuel pump, filter, and fuel pressure regulator, yet the problem persists.
Any 5.4 guys out there with an idea, I'm all ears. I'm out of ideas.