Strange wordpress search results?

I'm struggling with the search results my wordpress theme. I've added a ajax powered search with fallback to a single page, if no javascript is enabled. Basically my search.php asks if a certain post parameter is set, and if yes, only the results are returned. Else the whole site will be returned.

But the search delivers really strange results! Often post are found, which doesn't contain anything related to the search term and even dump searches like sdfsdf will return sometime a result. What is going wrong here?

The searchterm seems 开发者_开发百科to be found, as I can use get_search_query(); to print it out. Has anybody else encountered this before?

The search is probably looking for the search term in all of the content, visible and non-visible. Try repeating one of the searches that looked incorrect to you and view the page source (ctrl+u in most browsers), then find (ctrl+f) the search term and see if it turns up in a link or file name.