Is there a way to delete some search engines such as Ask.com completely from your browser? I absolutely hate it when it automatically changes.

Ask.com you had to install, however the path to the defaults are:

C:\Program Files (x86)\Mozilla Firefox\searchplugins

to specific ones that you might have installed are:

C:\Users\%username%\AppData\Roaming\Mozilla\Firefox\Profiles\xxxxx.default\searchplugins

Another easier solution is to simply click on the little down arrow next to your search engine bar to the right of the address bar, and then at the bottom there is " manage search engines.

Search engines do not change unless you change them or you install something, and are eager to install it and do not pay attention to the little tick box in the installer that says " make ask.com my preferred search " or whatever.

Ok thank you so much. That helped for what i needed.