Firefox hangs every few seconds with increased cpu usage

For the past month or so, firefox has randomly started hanging for a second or two at a time, while also having sporadic CPU usage, from 3-15 on an i7 while not changing pages or with any videos playing in the background. It will also freeze while typing making it difucult to type. Last time this happend I tried creating a new profile which didnt help, only moving the old profile and reinstalling firefox fixed it for a month. I've check for the sessionstore.jar but it's not there, i've tried safemode however it did not help the issue. The only Add-on's I have are Addblock and Greese monkey with youtube center. Turning off gresse monkey does not help and neither did reinstalling flash Any ideas besides reinstalling?