If you get ping spikes on a ethenet cable it is not likely a wifi problem.....unless of course you are actually using wifi when you think you are using ethernet. So as mentioned above disable the wifi in your machine do you are really sure.
Ethernet cables almost never get ping spikes. They can get data loss but the cable itself can not random delay data, it travels at some fixed percentage of the speed of light. Any delay would be the machine or the router not the cable itself.
So run tracert to some IP like 8.8.8.8
Next open a number of cmd windows and leave ping commends run to hop 1 and hop2 and any other you want. Hop 1 is your router and you should always see consistent low numbers. Hop2 is normally the ISP router...