CPU Unusual Overheating/Shutdown

Call_Me_Sir

Commendable
Feb 4, 2017
4
0
1,510
So, here's the story. I work remodeling an apartment building for those of the more wealthy persuasion. A few weeks ago, in the closet for the trash shout, I found a computer tower. I brought it home, and low and behold, it works! It even has all of my favorite games already installed! It looks like I've hit the jackpot, as I haven't had a computer in almost 2 years.
I realized soon after clearing out the programs I'll never use, that my treasure is flawed. Here's what I've discovered. I could really use some help, as this is the only devise keeping me sane while I'm at home.

Components:
MB: ASUS M5A97 EVO
CPU: AMD FX-8120
GPU: GTX 550 Ti
PSU: TR2 RX 750W
Interior and Exterior are clean and dust free
Not Overclocked
I've been building and repairing computers for personal use for 16 years, but I'm stumped...

I use MSI Afterburner with RivaTuner to monitor temperatures in and out of game, and Prime95 for stress test.

Issue:
While using casually, the CPU temp sways in the mid to high 50's, and idles around 30 degrees. Once I open Guild Wars 2, the temperature jumps to the 50's or 60's at the character select screen. I begin to worry once I choose a toon and enter the world. At that point, the temp spikes to high 70's and sometimes it reaches 85 and shutsdown. This happens with no warning, but, if I see the temp spike, and close the game, the CPU immediately cools down to the mid 30's.
BIOS reads temp around 30 degrees

I've Tried:
Reapplied thermal paste (repeatedly, multiple methods using Arctic Silver 5)
Stress tests resulting in shutdown within 2 minutes
Checked all components for fault or failure
Re-seated all connections
 

Call_Me_Sir

Commendable
Feb 4, 2017
4
0
1,510


I am running the stock fan, with two TT-2030 case fans and another exhaust on the back. I can't imagine that airflow is the issue.
I've downloaded and installed Overdrive now. Is there a way to set it to show temps in-game?
I ran a stress test through Overdrive, and I received the same results I described before.
 

Call_Me_Sir

Commendable
Feb 4, 2017
4
0
1,510


I found under Clock/Voltage in Overdrive, that Turbo Core was enabled. I disabled that, and it dropped the speed to the estimated 3100MHz.
I ran another stability test and when I saw the temperature reach 99 degrees, I immediately stopped it. The temp immediately dropped and is currently at 28.