autoHeight was deprecated in 1.9, and removed in 1.10.
Use:
$('#id').accordion({heightStyle: 'content'});
to auto size your inner div.
UPDATE:
I see that this is still quite an active post, so I decided to make sure my answer is still valid. It looks like this may no longer work in jQuery UI 1.11. It notes that the [content] property has been deprecated, and to use [panel] instead. Making the code snippet now look something more like this:
$('#id').accordion({heightStyle: 'panel'});
I HAVE NOT YET TESTED THIS, JUST FOUND, AND WILL RETURN AND REMOVE THIS COMMENT WHEN I HAVE TIME TO TEST