re: Ford truck/van with 4.6 owners. Crank, no start

So I go out there this morning. The battery was dead so I charged it.
The while on charger I ran some tests.
I had 12v to inertia switch and from. ( wasn't sure if that was the inertia switch so I felt for and pressed the button on the top. Not sure if it was tripped. No noticeable resistance on button. Go to driver module which is simple to find. It has power going to it on the white wire and no resistance on the black and orange wire.

After that I decide to just crank it again. I crank it and it starts right up. It runs like shite. Looping and idling rough. So I remember I had the intake completely off. I re-install and it runs good. Let it idle for fifteen minutes.
I had no scan tool so I cleared codes the old way. (battery disconnect, then hold start switch for 30 seconds)

No error codes came back.

Left it home today so I could test it more, but I'm thinking possibly a loose connection somewhere as I cleaned the connectors before testing them, (a practice I always had)


I feel it could be a failing inertia switch or module though. May just order both to be safe, and because they are cheap and seem to fail a lot on this vehicle.

I thank y'all for the help.

Was it raining yesterday when it wouldn't start? If yes I would at least take the FPDM off and look at the back side to see any moisture can get in anywhere.

The back side of the FPDM is aluminum and is bolted to the steel frame causing galvanic corrosion. The new FPDMs come with spacers/washers so the two dissimilar metals no longer make contact.

I'm still running the original FPDM. It's has had a piece of gorilla duct tape on the aluminum side of it for several years as a barrier between it and the frame. The FPDM had very little evidence of corrosion when I applied the duct tape. Some redneck preventive maintenance