I have a 2006 Dodge, Quad Cab, 1/2 ton, 4.7L,4WD, automatic. I bought 5 yrs ago with 63k miles. It now has 117,000.
First 18months I had truck it ran great-no problems other than normal maintenance.
Soon after, air conditioning stop working. Come to find out it was the PCM, replaced with refurbished PCM. AC worked again and the truck ran well for about 2 years after.
Then, check engine light came on. Misfire on 8 cylinder. After compression test, and leak down test learned that the motor was shot.
Little over a year ago I had my mechanic put in used 4.7L that came out of a Durango or Jeep Cherokee with about 75k miles on it--he said everything matched up with my old engine other than the oil pan, which he was able to modify.
Four weeks later, head gasket was shot, still under warranty- thank God! He pulled the motor out and replaced the head gasket.
Ran okay afterwards. A few months later, I went to pull our RV about 90 miles from our home. The truck really struggled like never before pulling the RV. We made it to our location. The next morning, after trailer was detached, started the truck and the rpm's really shot up for a moment and the check engine light came on. Next day had it checked-O2 sensor/heating element/ was what the scanner said. It was upstream-Cyl 1 bank 1 -he replaced both sides (upstream) and the check engine light cam back and said sensor was bad. He did not replace. He said I could drive the truck, until I could get to electrical specialist.
Electrical specialist said my PCM was bad. He could find no short anywhere between the 4 different O2 sensors. Due to COVID the PCM company I dealt with before went out of business. I kept driving the truck for several months until one day I stopped off at the store after work, as I began to drive home, after leaving the store, the check engine started to flash and the truck almost completely stalled out . I pulled over immediately, disconnected the battery, then reconnected -after a few minutes, started back up and the truck got me home with no problems. I then had the idea to put my original PCM -that I had saved, the one that has the ac issue. The same thing happened after I left work, stopped at the grocery store, check engine light flashed, pulled over, disconnected the battery, got home no problem.

Fast forward, I had both upstream O2 sensors replaced recently, scanner says the LIB1 1 is still bad, To this day, I disconnect the battery when I have to stop at the store after work. The truck runs really well if I do this. When I go to start the truck in the morning after 10 or 12 hours of being parked, the check engine light stays off and trucks runs well. If I drive straight to work, park for 7-8 hours, re-start and go straight home I have no problems-and check engine light stays off. If I cruise around the small town I live in, make a quick pit stop at the post office, etc; the check engine light comes back on. The truck doesn't stall out If I stay in my small town because I usually don't go over 25 mph, it idles higher when in park-1000-12000 rpm's rather than the normal 600-700 rpm's. When Monday rolls around, I pop the hood, disconnect the battery, then reconnect, and clears the check engine light. this is what I have been doing for about 2 months.

Any ideas what the problem could be would be appreciated?