When your preferred default search engine is switched to something else, what is it switched to? That may point to the source of the problem.

One possible culprit would be an extension. You can view, disable, and often remove unwanted or unknown extensions on the Add-ons page. Either:

• Ctrl+Shift+a (Mac: Command+Shift+a)
• "3-bar" menu button (or Tools menu) > Add-ons

In the left column, click Extensions. Then cast a critical eye over the list on the right side. All extensions are optional -- be suspicious of any related to searching. If in doubt, disable. If you didn't install it yourself or can't remember why you have it, you may want to remove it.

Often a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step.

Any improvement?

When McAfee, my preferred default engine, is replace in the tool, search menu, it is ether replaced by Yahoo or not replaced at all. In all cases the searches are functional. The problem s that I cannot get McAfee, my preferred search engine, work. I tried removing Yahoo from the list of search tools, but it still replace McAfee. I attempted to remove all occurrences of Yahoo, but I received the error, "Administrative Authority is Required".

I tried suggestions. They did not help

Could you copy/paste the address of the Yahoo results page to see whether it is the standard Firefox plugin for Yahoo or something else?

When setting the default search engine, the critical setting is the one at the top of the Search panel on the Options page. The others listed in the box are optional additional search engines you can use on a case-by-case basis if you like. However, some users reported that if you remove all of those, search becomes unmanageable. To reset to the standard ones, you can use the Restore Default Search Engines button below the box.

This is what you may be looking for. It is the information in the bar at top of screen.

https://search.yahoo.com/search?ei=utf-8&fr=tightropetb&p=test+query&type=23207_011517

In my last reply, the McAfee search engine was still in place. In the reply below, it has been removed.

https://search.yahoo.com/search?fr=mcafee&type=C111US0D20170426&p=test+search

Those both seem to be add-on driven search URLs. Could share your list of extensions with us? In order to include all hidden extensions, I suggest doing that this way:

Open the Troubleshooting Information page using either:

• "3-bar" menu button > "?" button > Troubleshooting Information
• (menu bar) Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter/Return

Then scroll down to Extensions and just below that heading, select the table with your mouse and copy it (either Ctrl+c or right-click > Copy), then paste it into a reply (either Ctrl+v or right-click > Paste). It will look a bit messy, but we're used to it. Thanks.

Past users with a search URL containing "tightropetb" mentioned that their startup page was hijacked to that address. Are you have that issue?

Here's my suggested procedure for tracking down and cleaning up that aspect of the problem:

(1) Open the Windows Control Panel, Add/Remove Programs. After the list loads, click the "Installed on" column heading to group the infections, I mean, additions, by date. This can help in smoking out undisclosed bundle items that snuck in with some software you agreed to install. Take out as much trash as possible here.

(2) Search for remaining issues with the scanning/cleaning tools listed in our support article: Troubleshoot Firefox issues caused by malware. These on-demand scanners are free and take considerable time to run. If they finish quickly and especially if they require payment, you may have a serious infection. I suggest the specialized forums listed in the article in that case.

(3) Investigate your Firefox Shortcut. The Firefox icon can be set up to launch specific pages at startup (or more specifically, when you use the icon). To check whether that is set:

First, open the shortcut as follows:

• Desktop shortcut: right-click the icon, choose Properties
• Pinned taskbar icon: right-click the icon, right-click Mozilla Firefox, choose Properties

Windows normally will select the Shortcut tab. If not, go ahead and click the Shortcut tab.

You'll see the Target highlighted. On 64-bit Windows, that usually is no more and no less than the following:

"C:\Program Files (x86)\Mozilla Firefox\firefox.exe"

If anything follows after that, try clearing it out.

After OK'ing the Properties dialog, you can test right away to confirm that Firefox now launches your actual home page. Either:

• double-click desktop shortcut
• right-click pinned taskbar icon, click Mozilla Firefox

Success?