You need to edit vbulletin_textedit.js in the clientscript directory as outlined in this thread.
https://vborg.vbsupport.ru/showthrea...t=smiley+space
You'll probably also want to download the uncompressed version of vbulletin_textedit.js by going to
http://members.vbulletin.com --> Download vBulletin and click More Download Options and look for the option to include the uncompressed javascript towards the bottom of the page.