show_404() doesn't use my custom 404 page

If your using latest version of CI3 will not work in sub folders

Code:

$route['404_override'] = 'error_pages/error_404_custom';

Try instead controllers > Error_pages.php

Code:

$route['404_override'] = 'error_pages'; // This will be a controller name

http://www.codeigniter.com/user_guide/ge...ile-naming

There's only one rule - please don't tell anyone to go and read the manual.  Sometimes the manual just SUCKS!