Ping spikes on wired connection

Venoox_1

Prominent
May 6, 2017
9
0
510
Lately my ping has been going up to 1000 ms and then back to 30 ms for 5 seconds every minute or so and it became really annoying. I decided to check with PingPlotter and these are the results:
3lhu1Wy.png

I used this program on other computers in the network and the results were similar. I decided to plug a laptop right into the modem and test it again and it turns out plugging in to the modem worked perfectly: no ping spikes.
I thought something must be wrong with my router so I bought a new ASUS RT-N18U and it didn't help.
Next I thought my UTP cables are damaged or something so I bought new cables (Cat 5e) too and that didn't work as well.
I'm running out of ideas and I would really appreciate it if you guys could help me.
 

Venoox_1

Prominent
May 6, 2017
9
0
510
I found out that if I disconnect my computer from my router physically then there's no ping spikes anymore, the moment I connect it back the ping goes up and down again (testing with the laptop). Then I tried disconnecting from my computer and plugged Wi-Fi adapter into the USB port and pink spikes appear again. It looks like something is wrong my computer but I don't know what.