Are there any plugins running in the tabs?

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do NOT click the Reset button on the Safe mode start window or otherwise make changes.

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

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

In Safe Mode, everything runs fine and I can confirm that add-ons are disabled.

However, as soon as I leave Safe Mode and return to normal, the resource use rapidly climbs.

I have also tried doing a re-install of FF, deleting all Library/preference files and starting from scratch. When doing this, the initial launch of FF runs hitch free, but when the process is closed and restarted, the lag returns.

I have a 4 core AMD A10 notebook, 8GBs of ram running Win 64 bit. * In my case, Firefox 19 uses up between 93% and 97% of CPU resources and it's not even open, it's closed....I've even checked the Windows Task Mgr and made sure the process was not running.

I'll shut down FF19 and be busy with other things and I return sometime later and Firefox.exe32* is maxing out my CPU. I'll open WTM to stop the process (Firefox.exe32*) and sure enough a short while later it's back maxing out my CPU again.

I've tried running Firefox in safe mode....same thing happens, tried uninstalling and reinstalling Firefox, again same result, I've reset the Firefox profile and started from scratch...no change. I've manually disabled all add-ons, extensions and appearance add-ons, still happens.

I've been using repairing and building computers since 1998 and this has me stumped. The strange thing is I also have a desktop running Win7 Pro 64 bit with Firefox 19 and it doesn't happen even with the exact same add-ons. I'm convinced it's something inside Firefox....everything else has pretty much been eliminated. If anyone can get a handle on this it would be greatly appreciated.

After my on-going problem stated above, I uninstalled Firefox 19 and installed Firefox 14 and the problem appears to be gone. I'm using the same profile as in Firefox 19, so no settings or add-ons were changed. Firefox 19 would self-start the Firefox.exe32* and max out my CPU.....I would shut it down in the WTM, but within 10 minutes it would restart, again maxing out my CPU.

Firefox 14 doesn't seem to have this quirk, I've left it on for hours and shut it down, it hasn't happened.....so I'll stick with this for a while until this gets straightened out. The problem with FF14 is that when you close it, it doesn't close, Firefox.exe32* continues to run (in WTM) and you can't reopen later without going into the WTM and ending it first......but at least it doesn't use valuable CPU resources. Who knows....maybe one day Firefox will work the way it is intended. I love the browser, I just don't like all the hassles and quirks.

UPDATE: Nope......it didn't work after all. What's most surprising is that I uninstalled Firefox completely.....but "Firefox.exe *32" still runs and maxes out my CPU. I've run Malwarebytes, Norton Antivirus and IObit Malware Fighter...nothing turned up. I guess next I'll have to run regedit and remove every entry in the registry that has the word Firefox in it. This is like dealing with malware or a virus! Either Mozilla Firefox is has a huge system resource sinkhole in its code or there is some sort of malware masquerading as Firefox.

OK!.........A SOLUTION AT LAST!.........I downloaded and ran a free antivirus/trojan program called "Combfix" and ran it after shutting off my anti-virus program. It runs through the command prompt, but you startit through windows like any other program....it's automated...easy even for a novice. It took about a half an hour and a reboot, but no more resource hog. I re-installed Firefox 19 and all is well. None of the other anti-virus programs I used found anything. Combo fix deleted about 12 files during its run and now my system runs like it should.........finally. I hope this tidbit of info helps others with similar problems.

I was having the exact same problem, running 19.0.2 on WinXPPro w/4 gb RAM; from the time I installed that update, everytime I opened FF, within 15 mins, CPU usage would be at 100% and I could sometimes not even get control back of the machine, but had to hold down the OFF button to do anything. I've just installed the latest update, 20.0.1, and I'm wondering if this bug is fixed, because I didn't see anything specifically about it in the release notes.

The fact that this happened on both a mac and a win machine says this really is a problem, not something I imagined.

I've had to start using Chrome (I'm certainly not going to use IE!) just so I can continue working (I design templates so obviously I have to be online all the time), but Chrome is vastly inferior; I had to install some system updates and then reboot this morning, and when I restarted Chrome, all my settings were gone; man I was steamed, and I want my FF back, but NOT to hog all my system resources!!!

Andria

I've left FF running all afternoon while I went out; so far, no CPU-hogging or sending the fan into hyperdrive, so maybe 20.0.1 has fixed that particular NASTY bug.

Thx!! Andria