when CPU maxs out like that it's not a FF problem but your O/S is corrupted causing that problem. Sounds more like a bad refurbished install.

In case you use "Clear history when Firefox closes" then try to disable this feature.

• Options/Preferences -> Privacy & Security
  Firefox will: "Use custom settings for history":
  [X] "Clear history when Firefox closes" -> Settings

Use one of these to close Firefox if you are currently doing that by clicking the close X on the Firefox title bar.

• "3-bar" menu button -> Exit (Power button)
• Windows: File -> Exit
• Mac: Firefox -> Quit Firefox
• Linux: File -> Quit

See also:

• https://support.mozilla.org/en-US/kb/Firefox+hangs

cor-el

I have not been using "Clear history ..."

It does not matter how I close the browser.

The problem seems to be connected to my bookmarks. I have found that I only get the crash when I save something to my bookmarks.

I also having another minor problem with bookmarks. When I try to drag a webpage to a folder in my bookmark toolbar, if I drag it to the bottom arrow, it immediately takes me to the bottom of the list. If I continue to drag it to the up arrow to get to a folder, the whole bookmark toolbar list begins move also to the left & is become hidden. Hard to explain here.

Are you using Sync to sync bookmarks?

If you use Sync then best is to disconnect Sync temporarily during troubleshooting.

You can check for problems with the places.sqlite database (bookmarks and history) in the Firefox profile folder.

• use "Verify Integrity" on the "Help -> Troubleshooting Information" (about:support) page
  in case errors are reported close and restart Firefox and retry

See also:

• http://kb.mozillazine.org/Locked_or_damaged_places.sqlite
• https://support.mozilla.org/en-US/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file

If "Verify Integrity" on the "Help -> Troubleshooting Information" (about:support) page cannot repair places.sqlite then remove all places.sqlite files in the Firefox profile folder. Firefox will rebuild places.sqlite and restore the bookmarks from a recent JSON backup in the bookmarkbackups folder.

• keep a backup copy of places.sqlite in case a new places.sqlite database has to be created
• http://kb.mozillazine.org/Unable_to_process_the_backup_file_-_Firefox

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

cor-el

Here's what was shown when I clicked Verify Integrity:

> Task: checkIntegrity + The places.sqlite database is sane + The favicons.sqlite database is sane > Task: invalidateCaches + The caches have been invalidated > Task: checkCoherence + The database is coherent > Task: expire + Database cleaned up > Task: originFrecencyStats + Recalculated origin frecency stats > Task: vacuum + Initial database size is 20480KiB + The database has been vacuumed + Final database size is 20480KiB > Task: stats + Places.sqlite size is 20480KiB + Favicons.sqlite size is 5120KiB + pragma_user_version is 52 + pragma_page_size is 32768 + pragma_cache_size is -2048 + pragma_journal_mode is wal + pragma_synchronous is 1 + History can store a maximum of 137249 unique pages + Table moz_origins has 8775 records + Table moz_places has 31037 records + Table moz_historyvisits has 6860 records + Table moz_inputhistory has 0 records + Table moz_bookmarks has 28790 records + Table moz_bookmarks_deleted has 0 records + Table moz_keywords has 0 records + Table sqlite_sequence has 0 records + Table moz_anno_attributes has 7 records + Table moz_annos has 101 records + Table moz_items_annos has 5775 records + Table moz_meta has 5 records + Table sqlite_stat1 has 16 records + Index sqlite_autoindex_moz_origins_1 + Index sqlite_autoindex_moz_inputhistory_1 + Index sqlite_autoindex_moz_bookmarks_deleted_1 + Index sqlite_autoindex_moz_keywords_1 + Index sqlite_autoindex_moz_anno_attributes_1 + Index moz_places_url_hashindex + Index moz_places_hostindex + Index moz_places_visitcount + Index moz_places_frecencyindex + Index moz_places_lastvisitdateindex + Index moz_places_guid_uniqueindex + Index moz_places_originidindex + Index moz_historyvisits_placedateindex + Index moz_historyvisits_fromindex + Index moz_historyvisits_dateindex + Index moz_bookmarks_itemindex + Index moz_bookmarks_parentindex + Index moz_bookmarks_itemlastmodifiedindex + Index moz_bookmarks_dateaddedindex + Index moz_bookmarks_guid_uniqueindex + Index moz_keywords_placepostdata_uniqueindex + Index moz_annos_placeattributeindex + Index moz_items_annos_itemattributeindex > Task: _refreshUI