Why does my MacBook Pro come to a halt when unplugged?

Hi,

My MacBook Pro Early 2011 seems to have suffered from some kind of liquid damage, and it slows down to a crawl if the power supply is unplugged. I saw a couple of other questions that seemed to relate, but difficult to work through so I am asking in this forum. Can anyone help me zero in the problem to a specific part that I need to clean or replace for this to be fixed.

I had taken this to genius bar in 2012 in Sydney and they said it could cost upwards of 500$ at that time. Since then, it has been pretty much sitting unused in my dad's house. It works absolutely fine when plugged in.

Am attaching Activity Monitor screenshots when the system is plugged and when it is not.

Thanks in advance

Harsha