Closed loop stall

I assume you have no codes? If we have not checked, let's start with that.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

If there are no codes then if this happens at the switch to closed loop then we have to assume we have a sensor issue. The sensor that would make sense is the upstream o2 sensors as most other are used during open loop as well but are run off a default program. I attached some info about this.

The best thing to do is monitor the o2 sensor data to see what it is telling the PCM. Then check the short term fuel trims and see if that is telling us something different. Since you already changed the ECM and sensors, it could be a wiring issue. However, let's see what the codes say or what the o2 are reading and go from there. Thanks

Two different mechanic shops have checked just about everything and are lost. There are some codes which the mechanics have been basing their diagnosis off of but all associated sensors and devices check out good.
I’m thinking it may be wiring or grounding issue because of the corrosion throughout the underneath of the truck (it lived in Syracuse, New York about for 10 years).
I’m going to pick it up from shop when I get back in couple of weeks and begin checking grounds and wiring as much as I can without having to begin changing wiring harness for further trial and error.

Thanks

Okay. Sounds great. However, if you can make sure they write down all the codes they found because that will point us to the specific systems which will limit down the wiring that is possibly the cause. Also, we can see if they possibly missed something.

Just let us know whenever you get back to it and we can go from there. Thanks for the update.