I've been dealing with a stubborn-to-open passenger door since I purchased my new-to-me bronco II.
Both doors were sagging, so I had the hinge-pin bushings replaced.
The body guy adjusted the door latch, but the problem seemed worst.
If you slowly close the door, you will get a feel for the alignment of the door latch.
With patience, you will identify any sort of up/down movement when closing.
I adjusted the latch, eliminating any movement but problem persisted.
I then focused on the exterior passenger handle...it had noticeable play/looser feel.
I pulled the door panel, and identified a rod that gets pushed down by the exterior handle. I reduced the amount free-play, by carefully straightening the rod.
I imagine over the years these door-mechanism rods compress...creating free-play.
Even with free-play removed, passenger door would not open from the outside.
Only way to open the door is to lower the glass and give it a pull, or with the interior handle and some persuasion.
Last resort was to try some lithium grease on the latching mechanism...problem solved
With the latch aligned, passenger door now closes and opens effortlessly.
To-do list on my bronco is getting shorter and shorter...cheers
