1. Remove a possible user.js file https://support.mozilla.org/en-US/kb/how-to-fix-preferences-wont-save#w_user-js-file-overriding-preferences
2. Remove any delta related programs from the control panel.
3. Use the searchreset tool after

• https://addons.mozilla.org/en-us/firefox/addon/searchreset/

• http://info.delta-search.com/uninstall/firefox.html
• http://deletemalware.blogspot.com/2013/07/remove-delta-homescom-removal.html

• [/questions/949921]
• [/questions/943111]

Hello friends! my name is Naveed.

Tips to remove delta search from mozilla firefox permanently.

In case you open a new tab in Firefox, and the search you wish to remove still appears after removing from Addons, please do the following:

1. Type in the address bar line "about:config" and press enter. 2. Confirm the message. Type the name of the search you wish to remove in the search bar ex: Delta Search. 2. Right-click the entries and click Reset. Restart Firefox.

That's if the problem persists reply to this I will get back to you.

Quick Fix (partial)
I have not tried this but from Firefox 23 onwards the search is controlled by what is used in the searchbar (top right by default). If you change the search engine used by the search bar it should work and it should change the search used in other places such as in the navigation bar.

Full and Permanent removal
Again I have not tried Naveed's method. However the method is changing Firefox preferences and is NOT removing the rogue software. See the links in the helpful reply above for full instructions.