are you getting high CPU usage from plugin-container.exe in firefox and maybe there is a virus or a trojan 
i noticed that lately my computer fan has been going off high. so i look at the performace monitoring and it shows that firefox plugin-containter.exe is using really high cpu. so i blocked it with my norton firewall and some of the sites doent work, like when i go to youtube the sound does not play, so when i allow it in the firewall, the cpu goes off again. i think whats going on is updating whatever extensions i have installed.