Why won't my car door stay shut?

Just get in there with a screwdriver and start fiddling around with it. I doubt that you can do any damage, as long as you don't pry too hard with extreme force. Besides manipulating the latch (pushing, pulling, and prying) with the screwdriver, try working the door handles (inside and/or outside) while you are simultaneously working the latch with the screwdriver. Eventually, you ought to get it unstuck this way. Spray a little WD 40 or other penetrating oil on the lock mechanism while you are at it.

It's got a rolling cam double latch.

Hold the handle up as if you were opening the door.

Now, take a screwdriver and roll the latch mechanism open on the door latch cams.

Oh, and spray the snot out of it with wd40 or equivalent.

ADDED:

If you tried SLAMMING the door a few times, you may have shifted the latch pin on the door pillar back too far,and you'll need to readjust the pin forward a little bit.

Know-it-all has the correct answer for getting the door to latch, but WD-40 just acts like a dust magnet.

Use powdered graphite and just squirt the powder into the lock cylinder.

look at the latch...is it closed?? if so its not opening when door is opened......which means a spring inside latch is broken most likely.....

only real way to fix this is to replace the latch....u can get a new one form a junkyard or parts store......but it is some amount of work to install it......

** could also be the linkage to the latch that has broken....

** need to pull the door apart to find out what exactly is broken then replace whatever those parts are....

spray wd 40 in it, work it aroud a couple of times or

apply grease in it (the mechanism and the post)

make sure your seatbelt is not doing it

DUCT TAPE!