navigation links not working

I’m using <?php query_posts ('posts_per_page=4'); ?> to get posts for a custom archive page and <?php posts_nav_link('sep','previous ','next '); ?> to create nav links to page through multiple pages of posts.

the problem is that I’m not going through the older posts. So if I go to site.com/?page_id=42 it shows posts 8 to posts 5. Then if I click on next to go to site.com/?page_id=42&paged=2 it still shows posts 8 to 5 instead of posts 4 to 1.

[Please post code snippets between backticks or use the code button]]