How do I keep a door from closing on its own after opening it?

I hope this does not sound silly... but do you remember these (see pic.).. I mean... work great for some applications (found at any home improvement store).

I doubt this will help any but wanted to offer something. Good luck.

The door jam on the hinge side is not plumb. Place a 4' level on the wall along the hinge side jam. Then place it on the door stop of hinge jam. If either or both of these are out of plumb the door will tend to swing open or closed depending on which way the jam is out of plumb. The only correction is to plumb the hinge jam. This will probably require removing the casing around the door and resetting the jams.

Take the 1 or more of the hinge pins out,, then take a hammer and bend the pen some what, what this does is tighten the swing up on the door, this should solve your problem

As for taking the door out... theres no point because the door jamb just copies what the framing is. The hinge pin trick will work.