can't add error page when disable the module

I disable the module, delete it from the module directory but i can't put any page in my settings, i create and set a page to display 404 error but it redirect me in the home page only search/node/ page work,
in the .install file

<?php

/**
 * Setup Search 404 by changing Drupal's 404-page to search404.
 */
function search404_install() {
  search404_enable();
}

how to disable the search404 function after uninstalling the module

Thanks