hello danei, can you replicate this behaviour in firefox in safe mode too?

Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

Yes, it also happens for safe mode, at the 1st try.

does it make a difference if you disable all your plugins under firefox > addons > plugins temporarily? (not extensions, since they won't be active in safemode anyway)...

All plugins disabled in safe mode, still no luck...

ok, this sounds strange - could you decribe your system's setup a little bit more: what kind of hardware you're running, what security software is used, are you using a dual-screen setup by any chance, etc...

Hardware: thinkpad sl400 CPU: E8135@2.66 GHz RAM: 6G ddr2 Graphic card: nvidia G105M 256M Display: only built-in lcd @1280*800

Software: Windows 7 sp1 64bit ultimate, fully updated Microsoft Security Essentials (turn off protection makes no difference...)

Any other info needed?

i'm pretty much clueless - i also didn't find any existing bug that resembles your symptoms... since when is this problem happening - did it change after an update (by firefox or windows)?

Did you manually disable all plugins because Safe Mode doesn't affect plugins?

• https://support.mozilla.org/kb/Troubleshooting+plugins
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Try to boot the computer in Windows Safe mode with network support (press F8 on the boot screen) as a test to see if that helps.

I'm not sure about when, because I often leave fx window visible. I accidentally left fx minimized for hours several days ago and when I was back my machine was as hot as an iron.

I don't remember the issue was there before version 20. I may try v19 another time.

@cor-el: Yes I tried disabling all plugins, with no luck. I may try safe mode another day. For now, so much work to do...

@philipp Fx 19 is fine. @cor-el Booting into safe mode doesn't help.

• kb.mozillazine.org/Memory_Leak

@iamjayakumars: You don't read, do you?

Lets see if we can do any thing to get it to not use high CPU.

1. Set Firefox to start from a homepage, and set that as about:blank
2. Make a new additional clean profile
   • Profile Manager - Create, remove or switch Firefox profiles
3. Boot into Windows safemode without network support
4. Start Firefox in Firefox's safe mode, with all plugins disabled in the new profile
5. Now check CPU usage, it should be normal and minimal. Give it a minute or two.
6. Now minimise does it still increase ?

• How are you checking CPU usage ?
  (Task manager or something more sophisticated ? )
• Is nearly all the CPU usage from a single firefox process ?

I am also wondering if it may be worth considering the possibility of a malware problem.

@John99: Ok, last time I tried booting into safe mode with network and it didn't help. And I just tried your approach and still, no luck...

I use windows' builtin task manager to check cpu usage, sysinternal's process explorer shows identical result. Single firefox.exe boosts to use about 20%~50% cpu when minimized, and since my cpu has 2 cores, I think it means fx takes 40%~100% cpu time of single core.

I don't think it's about malware, because fx 19 (even when using my current profile in normal mode in normal windows state) doesn't have such issue. And I've tried downloading fx20 and extract files to another place and problem is still the same.

Did you check in PE which thread (if one specific) is taking up that CPU usage?

Do a clean reinstall and delete the Firefox program folder before reinstalling a fresh copy of Firefox.

Download a fresh Firefox copy and save the file to the desktop.

• Firefox 20.0.x: http://www.mozilla.org/en-US/firefox/all.html

Uninstall your current Firefox version, if possible, to cleanup the Windows registry and settings in security software.

• Do NOT remove personal data when you uninstall your current Firefox version, because all profile folders will be removed and you will also lose your personal data like bookmarks and passwords from profiles of other Firefox versions.

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

• It is important to delete the Firefox program folder to remove all the files and make sure that there are no problems with files that were leftover after uninstalling.
• http://kb.mozillazine.org/Uninstalling_Firefox

Your bookmarks and other profile data are stored in the Firefox profile folder and won't be affected by an uninstall and (re)install, but make sure that "remove personal data" is NOT selected when you uninstall Firefox.

If you keep having problems then also create a new profile.

• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Profile_backup

• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Clean_reinstall

Do a malware check with some malware scanning programs on the Windows computer.
Please scan with all programs because each program detects different malware.

Make sure that you update each program to get the latest version of their databases before doing a scan.

• Malwarebytes' Anti-Malware:
  http://www.malwarebytes.org/mbam.php
• SuperAntispyware:
  http://www.superantispyware.com/
• Microsoft Safety Scanner:
  http://www.microsoft.com/security/scanner/en-us/default.aspx
• Windows Defender: Home Page:
  http://www.microsoft.com/windows/products/winfamily/defender/default.mspx
• Spybot Search & Destroy:
  http://www.safer-networking.org/en/index.html
• Kasperky Free Security Scan:
  http://www.kaspersky.com/security-scan

You can also do a check for a rootkit infection with TDSSKiller.

• http://support.kaspersky.com/viruses/solutions?qid=208280684

See also:

• "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked

@cor-el: Ok, see screenshot: http://i.imgur.com/wDzvfH7.png

I've tried reinstalling fx already. No luck.

I've MSE installed and running so I don't think it's a virus problem. If we go into this direction, next step will be to re-install the system clean, and change my hardware part by part. That would be too far and useless.

I've noticed that if I open enough tabs where the "+" sign flashes indicating tabs are going beyond the screen, then firefox seems to start hogging cpu, even after tabs are closed. If I only open enough tabs to max out the tab bar but NOT have any go past the "+", then firefox idles at 0 cpu no problem. If I repeatedly open tabs to go beyond the "+", close them down, etc, etc, eventually firefox starts eating all spare cpu cycles, making cpu max at 100%. It does this even after I've closed all other tabs, and just have 1 left open. I wait to see if maybe some kind of garbage collector or memory manager or something will kick in, but it just keeps hogging the cpu even though nothing is going on (eg: just sitting on google's home page). I've disabled add-ons, plugins, etc. I used the Help > Troubleshooting Information > Reset Firefox button to reset my profile. I've opened in safe mode. I switched off javascript. Tried lots of things, but still got same result.

The cpu hogging gets so aggressive that other programs will start getting interrupted (eg: win media player will start "skipping" the mp3 playing, b/c it's fighting to get enough cpu time to play it fluidly).

I'm using WinXP on an old Dell POS celeron box w/ 1gb ram at work. It's old, but I haven't had problems with Firefox doing this on the comp until 20.x upgrade.

You should still do a malware check because it sounds that Firefox is doing some tasks in idle mode.

Did you already create a new profile directly (i.e. not a reset)?

• http://kb.mozillazine.org/Profile_Manager
• https://support.mozilla.org/kb/Managing+profiles

Do a clean reinstall and delete the Firefox program folder before (re)installing a fresh copy of the current Firefox release.

Download a fresh Firefox copy and save the file to the desktop.

• Firefox 20.0.x: http://www.mozilla.org/en-US/firefox/all.html

Uninstall your current Firefox version, if possible, to cleanup the Windows registry and settings in security software.

• Do NOT remove personal data when you uninstall your current Firefox version, because all profile folders will be removed and you will lose all personal data like bookmarks and passwords from profiles of other Firefox versions.

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

• (32 bit Windows) C:\Program Files\Mozilla Firefox\
• (64 bit Windows) C:\Program Files (x86)\Mozilla Firefox\
• It is important to delete the Firefox program folder to remove all the files and make sure that there are no problems with files that were leftover after uninstalling.
• http://kb.mozillazine.org/Uninstalling_Firefox

Your bookmarks and other personal data are stored in the Firefox profile folder and won't be affected by an uninstall and (re)install, but make sure that "remove personal data" is NOT selected when you uninstall Firefox.

If you keep having problems then also create a new profile.

• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Profile_backup

• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Clean_reinstall

@cor-el: a malware that infects only firefox 20 but not 19 or any other program, and MSE scan cannot detect doesn't sound any logic to me.

As for those profile and re-install things, I've done so many times in so many way for at least 3 different versions and I'm tired of these.

I hate to give up here but I say you've done all you can do and there's no shame in stopping here.

You can try a different browser like Google Chrome and hopefully get better results.

Although you say you've tried many new profiles and Firefox Safe Mode. I'd like to mention one thing you may have overlooked. Plugins. Plugins are different than addons and are not disabled when using Firefox safe mode, only the add-ons are disabled.

I know you said you already tried this here but just mentioning it in case you didn't do the way I explain it below.

So you can try disabling all your plugins individually and surf for a while and see if there's a difference: Tools > Add-ons > Plugins

I suspect it's a plugin b/c you have 103 processes running in your screenshot above. I'm not saying that's the most I've ever seen but it feels like there's one too many programs running at the same time. So it feels like a plugin is hooking into Firefox.

You can keep trying to solve the problem if you like Firefox that much. But it's looking grim in my opinion.