Jim,
I have found that usually when the door no longer stays open, all of the hinges need replacing. You can remove the hinge and identify a bad one by comparing it to a new one. I buy hinges in a lot of twenty at a time and keep them in the coach and replace them as necessary. I have been fulltiming in a 2000 Marquis for 8 years, and I have probably replaced every hinge in the coach, or close to it with some more than once.
Gerald