door adjustment

Well once more I have to drive my mustang in the winter. Two days ago I was driving my car and everything was good. I did not have any problems with my door at all. Now last night I went to open my door and it makes a popping noise. After doing some checking its my door (bottom part)hitting the fender. I don't know why it would do this at all. When I get in and out I never push down on the door and I am the only driver.The door does close all the way and the way it always has. How can I adjust the door or is something else I need to look at?

Last night I tryed to see if there was any play in the door by picking it up and it seem okay. I will take a look in the day light to make sure. How hard is it to replace the bushings?

I guess I will get dress and see if thats the problem. Thanks for the info!!!! I will post if thats problem or not.