Check fuel pressure.

 

Fuel pressure is perfect. Holds strong at 58psi through everything.

I do notice a slight smell of exhaust from under the hood. Going to pull the heat shield off of the manifold and see if we have a crack anywhere.

 

Open a can TRANS TUNE

 

Just bought a can and have it idling in the driveway now. Even though shifting into gear stalls the motor, would you think that would yield a higher benefit than just idling in park?

 

Quick update:
Have been idling with the trans tune in the transmission for a couple hours. Have tried to go out and hold the rpm at around 1-1.5k for short intervals. Shifting out of park still results in an engine stall but far less violent than previously observed.
Out of curiosity, I performed a few tests of holding the idle above 1000 when shifting. Still resulted in an engine stall.
However, if I did the same thing with the transfer case in 4 low, it would shift and allow the vehicle to move until it came to a full stop, then it would stall almost immediately.
I shifted back to 4 high, and retried the above steps. This still resulted in an engine stall without vehicle movement.

For piece of mind, I have purchased a new AC Delco throttle body. I know this is probably not the fix, but it is the only part I have cleaned and not replaced, so I wanted to cross it off the list. Will re-test after installing.

 

I have now replaced the throttle body. Idles beautifully now. Still seeing the issue with stalling when shifting out of park.

I did some more testing and after many attempts, finally got the transfer case into neutral. Shifting into all drive gears is possible without stalling.
Shifting the transfer case into and out of 4 low results in an audible thunk sound and it shakes the vehicle. Also worth noting that sometimes shifting out of 4 low to 4 high fails, with the second or third attempt finally causing the 4 high light to illuminate.

 

Post a video (with sound) pointed at the IPC showing stable idle then stall.

 

Drive it like you stole it to clean the solenoids.

 

a faulty torque converter can potentially cause an engine to stall when shifting to drive, particularly if the converter is severely worn or malfunctioning, leading to improper clutch engagement and causing the engine to lose power at the moment of shift transition.

Key points about a bad torque converter and stalling:

• Slipping clutch:
  A failing torque converter can cause the clutch to slip excessively, preventing proper power transfer to the transmission, which can result in stalling when shifting to drive.
• Fluid issues:
  Internal problems with fluid flow within the torque converter can also lead to stalling, as the converter may not be able to properly engage the clutch due to insufficient hydraulic pressure.
• Locked converter:
  In some cases, a faulty torque converter can become locked up, which can cause the engine to stall when transitioning from idle to drive.

Other symptoms of a bad torque converter:
Loss of acceleration, Rough shifting between gears, Engine surging or vibration during acceleration, and Increased transmission fluid temperature.
https://advancedtransmission.com/sym...s%20stationary.

 

Got about 6 inches of snow this afternoon, so my work is paused.

I was able to confirm that with the transfer case in neutral, I am unable to spin the driveshafts. Also, putting the transfer case and transmission in neutral, I am unable to push the vehicle.