Lean Condition Begins 60 Seconds After Startup - Recent Rodent Damage

Looking for help, or wild guesses, on why my engine develops a lean condition at 59-60 seconds of run time. 2015 Tundra, 5.7L 3UR-FE engine. This occurs during both cold and warm starts and is repeatable right at the 60 second mark. For the first 59 seconds the truck runs smooth, and short fuel trims are between 0 to -10%, both banks. At the 60 second mark, fuel trims jump to +20% and it idles rough and misfires on any/all cylinders. Similar if I try to drive it, fine from 0-59 seconds, but trying to move forward after that it immediately stalls.

Background: The truck sat for a few weeks and I had rodent damage which required removing the intake manifold to replace the knock sensor wiring harness. They had also nested in the air intake box under the filter, and also above the cabin air filter. When I did the knock sensor harness my battery was disconnected to clean the terminals, so the ECU lost all of its learned settings (unsure if relevant).

Things I’ve tried: First, to track the idea that obviously this must be caused by a vacuum leak from my intake manifold removal, I replaced the intake manifold and throttle body gaskets, smoke tested the vacuum lines (no leaks noticeable). Also tried the carb cleaner/propane tests, nothing noticeable. I blocked vacuum lines to the intake one-by-one (PCV tubes, crankcase ventilation hoses, fuel purge valve hose), no change in behavior. I’ve hooked up a pressure gage to the vacuum line and read 22 in Hg at idle upon startup. At the 60 second mark, this momentarily drops to 20 in Hg then settles back at 21 in Hg.

To test the idea that this might be caused by the ECU reset, I cleaned the MAF and throttle body. Tried running with a disconnected the MAF sensor, and it stalls immediately at 60 seconds instead of just getting rough. Tried running with disconnected AF sensors and it's similar to the MAF, does not fix the problem.

It seems to me either there must be a vacuum circuit that is not connected until 60 seconds in, or there’s other rat damage I have not been able to find. Current DTC codes are P0171 and P0174 (system too lean, bank 1 and 2), P1603 (engine stall history), P1605 (Rough Idling). I have had misfire codes for P0300 through P0308, though they don’t come back very quickly after clearing the codes, I can see in Techstream that misfires are occuring. I can also see in Techstream that I enter closed-loop operation well before the 60 second mark, which was my original thought on why the engine runtime is repeatable. Maybe I need to check the fuel system, but I’ll point out I can constantly rev the engine during the first minute, but the issue still starts at 60 seconds of run time, rather than being dependent on the amount of fuel used.

Anyone have ideas on what might be causing this or what I should check next?

 

Looks like it’s an issue on the fuel side. Measured the pressure and get 20 psi, then once 60 seconds passes it trickles down to about 2 psi.