I just got a new computer with Windows 8 four days ago.  Almost immediately, I noticed the machine was running slow.  Upon checking my performance through Norton, I found the pesky little tiworker.exe was eating up 99% of my CPU.  Angry, I contacted a Microsoft tech through chat.  He told me there was nothing wrong with Windows to cause the problem, that it had to be a third party program running somewhere that was causing it.  When I reminded him that tiworker.exe related to Windows Updates, he still insisted there was nothing wrong, and to contact my computer manufacturer, which I did.

The great guy at HP told me that Microsoft was "full of baloney" that there were virtually thousands of posts throughout forums on the internet related to this problem, and it was probably not related to their hardware or software or any other third party software.  He advised me to remove all of the extensions in Google Chrome (which I was using when I discovered the problem) which I did, but no improvement.  After checking a few other things, it dawned on me to try Mozilla, to see if that presented the problem.  I did, and it did NOT.  We therefore concluded that I had a corrupted Chrome, and that I should uninstall it and reinstall.  I did.  Guess what, NO MORE PROBLEM.  Hooray!

I shut down the computer that evening after doing yet another Windows Update (I had done an hour's worth the second day I got the machine, and a few minutes worth while online with the HP tech.  This was the 3rd one in 3 days).

This morning, I booted up, and noticed quite a hang in Chrome.  Upon checking, I found that DAMNED file, tiworker.exe, happily chomping away at my CPU at the tune of 60%.  Same thing in Mozilla.  OH CRAP.

I then went out  to have lunch with my friend, frustrated as hell, determined to get to the bottom of it when I returned.

I  returned after being away for 4 hours.  The computer had been asleep for about 3 of those hours.  When it came back to life, Chrome was running, and after checking my e-mail for 10 minutes, I decided to check my performance.  Guess what???  NO MORE tiworker.exe.  I closed Chrome, opened Mozilla, played around a bit in it, checked my performance, and???  NO MORE tiworker.exe.

I am totally convinced that the tiworker.exe problem is closely related to Windows Updates, and that MICROSOFT SHOULD DO SOMETHING ABOUT IT, to prevent it hanging on for many hours after an update is completed.  Their software has a serious bug in it that nobody wants to fix in a way that everybody can benefit.  PLEASE, Microsoft, FIX THIS once and for all! 

It could be that tiworker.exe doesn't actually have a problem and is just doing exactly what it's supposed to be doing.

I noticed something similar last month, however someone here kindly looked at a xperf file I uploaded and found that tiworker.exe was carrying out a cleanup of the WinSxS folder by compressing files to free up space.  After just letting it run in the background for a few hours, it finished doing what it was doing and it hasn't bothered me since.

Here's the original thread on it:

TiWorker.exe Excessive CPU Usage After Windows Update

If the link from AnaBna doesn't explain your issue, run a xperf trace with the commands I posted there.