Almost every game is lagging

[Thanics]

My ASUS GL702v laptop is now causing: (GTX 1060)
FPS drop from 60 to 15 suddenly while playing games , it persists for a few mins then disappears then comes back again
I tried updating gfx driver, installing throttlestop and disabling turbo boost - didn't work
ran malware bytes.
I was disappointed when it lagged when i played RUST(even on potato settings)

Update 1: If i take out my charger and plug it back in it runs normally again to only get sucked back by the fps drop .
Update 2: I have followed this thread and still the annoying frame rates occur still. I've breached the motherboard opened heatsink and it looked similar to this video

 

[J_E_D_70]

Sounds like heat issue on either cpu or gpu.

 

[Thanics]

Sounds like heat issue on either cpu or gpu.

Temperature before lag was 81 and after lag was 77 celcius,
Before lag, perfcap showed pwr , after lag it showed pwr,thrm in gpu z. How do i stop it?

 

[J_E_D_70]

Did you clean and apply thermal paste after opening it?

Did you follow the thread within the thread about stopping turbo from kicking in? How far did you undervolt cpu and gpu?

 

[Thanics]

Did you clean and apply thermal paste after opening it?

Did you follow the thread within the thread about stopping turbo from kicking in? How far did you undervolt cpu and gpu?

I opened the heatsink and gathered some left overs back to the center and spread the old thermal paste using teflon coated instrument (I shouldn't have done that) anyways......The thermal throttling is definitely heat issue both in CPU and GPU.
My questions is :
Should I replace the heatsink?
Is there a custom built fan for this laptop dissipate heat at larger quantity?
Is reballing needed?
Normal rubbing alcohol and cooler master thermal paste is good right?
OR
should I give to a service center?

Yes I stopped turbo boost but recent bios update fixed that issue (so its useless anyways) Cpu undervolt -.150 v i think. GPU as given in link 900 to 1600 core offset curve

 

[AniChatt]

Pls don't under volt or disable turbo boost just for a reason it is not dissipating heat properly.
First as you have already opened the heat sink, clean the area with isopropyle alcohol and then apply any good quality thermal paste then install the fan again. Clean the vents with pressurized air to remove any dust that might hinder proper airflow.
Please do not spread old thermal compound by any means. It will make things a bit more complicated. Clean it for all cost and apply new good quality like arctic or cooler master thermal compound.
If you are still facing thermal throttling then go to service center.
It is not a custom PC to experiment with, a laptop is way to fragile for experimentation. So don't try to purchase any crappy heat sink (since you don't know as it is not a branded one).
Go to service center for a quality repair. However I don't know if you have voided the warranty already by removing the heat sink.

 

[Mark RM]

From reading this through it seems a really straight forward thermal throttling issue.

The number one most failed component on laptops is the heatsink. If the unit is under warranty I'd send it in for overheating, if it's not I'd replace the heatsink and both fans with new ones.

The only one I see on Ebay is a used one, I wouldn't buy it unless I was really desperate. Asus must have a source to locate such items.