Misfiring issue

All,.

Seems I am having an issue with 02 explorer 4wd 4.0 ltr. engine, 78000 miles. The issue comes up when the vehicle has sat for a while and it has rained quite a bit. When we go to drive it, that is when it acts up. It runs fine with no issues when it is dry out or rains a little bit. After a rain storm, if we drive it, it runs fine for maybe 2 or 3 miles then acts up. IT is never right away after starting. it is random and the last time it did it it was driven a couple miles with no issues and then parked then on the way back it started to misfire. The check engine light flashes telling me it is misfiring and the truck lacks power as it won't go very fast when you step on it. It wants to stall when stopped. IF you put it in nuetral or park it stops and idles and rev's fine so it seems like it load related. This will happen for a few miles and then will go away and drive fine and not reappear until it rains again. I have had it to the garage but they couldn't find issue as it was not doing it and no codes were present. I have installed new plugs and wires and also a new ignition coil. I have went out there at dark and completely hosed down the engine compartment and windsheild with a garden hose to soak everything. No evidence of arcing and it didn't cause the misfire issue. I also hosed down the underside good and that didn't cause it. The last hard rain it did it again after hoping the new ignition coil would work. IT didn't and it misfired and the check engine light lit. Below are the codes set when I scanned.

Po152 - High voltage bank 2 sensor 1
PO175 - bank 2 system to rich
PO300 - Multiple misfire detected
PO306 - Cylinder 6 misfire

NOt sure what to check next. I am assuming because this is water related it is probably an electrical issue somewhere, just not sure where to look next beyond plugs wires and coil. the strange thing is it goes away shortly after it happens so troubleshooting time is minimal. Any thoughts would be greatly appreciated. If I can't find issue, I Will need to wait until next rain storm and drop of at the garage. THx a bunch

I suspect the trouble is in the B2S1 circuit or the sensor
itself. It seems to be sticking in the rich (high voltage)
area and the PCM is leaning that bank and causing the
misfires.

Since it's raining when the trouble shows, the high humidity
might be causing more water vapor in the exhaust and
affecting the (failing) O2 sensor.

That's a theory anyway. I'd inspect the sensor wiring,
and if it's OK then replace the sensor itself. The cost would
be less than a garage diagnosis anyway...

Ok. Do you where this sensor is located? Thx

On your 2002, the sensor will be the upstream sensor on
the driver's side. It should be located on the header pipe
underneath the driver's side header. You may have to
remove the rubber fenderwell to access it, or it might be
easier to reach it from underneath the vehicle...