Alright. I've got a very persistent lean code on both banks, along with knock sensor. Note: Knock sensor code only comes on if truck is driven hard, I assume from lean condition pinging.

Background: 2002 4.0, about 200k miles. Non SAI

Complete reseal of top end-Besides injector o-rings.

No known vacuum leaks.

Has new MAF

New upstream o2s (Bosch)

New fuel pump (actually replaced due to lean codes while accelerating a while ago)


So, where shall I start? I've read something about PCV valve being the cause. Being that the injector o-rings are original, would it be worth it to replace them? I can have the entire upper intake off and on within an hour, so easily replaceable.

Thank you in advance.


Edit.. Truck runs perfectly! No misfiring, no power loss, just got 15.6MPG in 60% city driving 40% highway at 55.

 

Bringing this back again. Lean codes still here, replaced the injectors and the old seals definitely looked like they were part of the cause, but still have a lean code.

Could a bad brake booster be leaking vacuum? The brakes have always been spongy, but stop fine and foot to the floor will activate ABS.

 

You probably have an air leak in the system, best bet is to get it smoke checked by a shop