Ping lag and stutter UPDATE Still need help!

Specs:
i5, 8GB Ram, R9 290, Win8.1

While playing TTT, I get a stutter every 10-20 seconds making it difficult to play.
Using the net graph, you can see the ping spike (lowest red bars)eg.

I have another machine and this problem does not occur there(same network)

I tried;
validating files, steam said 2 failed and downloaded them
moving from a HDD to a SDD
quitting the wireless adapter software
checked Windows Firewall
switching server
switching gamemode
disabling addons

Any ideas of what could be causing the problem would be greatly appreciated

UPDATE:
Reinstalled Gmod, issue is still there
Ran Gmod in Safe mode with Networking, no ping lag
This leads to believe a different program/s is causing
Any help on how to identify this program???

Also happening with tf2

Could possibly be the cpu/graphics card overheating or failing. Do you happen to have any others lying around or have a friend that can spare you one or the other for testing?

Sorry, completely forget about this thread after fixing the problem!
I used a power line adapter to connect to Ethernet and the issue is gone
Thanks for the help though