FYI on my own SP2 over the months, I've also noticed different processes consuming CPU utilization when idle (causing the unit to heat up and run the fans), which included:
- Microsoft Windows Search Indexer -- happens periodically, which is normal I suppose, but it seems to always struggle near the end (ie. it would take a long while and spike up the CPU to finish the last few hundred items to be indexed); I'd tried to rebuild the index but the same behavior continues
- Antimalware Service Executable -- also normal I guess, although I've seen it spike CPU even outside scheduled scans (must've been scanning complex items in real-time?)
- Communications Service -- I guess it's related to the Win 8.1 Mail app, which also seemed to struggle a lot, getting stuck updating mailboxes and spiking CPU in the process? Note I was testing with Exchange Online, Outlook.com/Windows Live Domains, and Google Apps for Business accounts all using the same email address on my domain, which I guess can get confusing. Also tested old-school IMAP server accounts with 100+ folders...
- Apple IE DAV -- it's the iCloud bookmark sync to IE, which has had a lot of problems with the Win8.1 IE11 on the SP2 (a known problem?). It often got stuck and spiked CPU a lot but actually failed to sync with IE, whereas the iCloud bookmark sync to Firefox and Chrome (which use browser extensions) are more reliable. I finally got it SEMI-WORKING after deleting all browsers' bookmarks and starting from scratch, and not adding any bookmarks with a long title or weird characters. Except, while IE will now see bookmarks added via Firefox or Chrome, adding bookmarks via IE itself won't be seen by the iCloud sync and thus wouldn't get added to Firefox/Chrome.
- photoshop gpu sniffer (I forget exact name) - always hung and spiked CPU after opening Photoshop CC (though I think Adobe's latest update has fixed the problem?)