Drawdown fps, after replacing the graphics card.

Hello!

At a similar forum for the first time, but the situation calls for, so maybe something will be not clear, and not written, sneakers do not rush.

My computer was a GeForce GTX 660. There were no problems. At all. Started playing PUBG and became sad fps (25-30 with just one monitor). Got a new computer with GeForce GTX 760. Decided to replace this, but then the problems started. Overall fps went up (40-60 with two monitors), but at a random time, drops of fps in 2 times, right in the middle of the game for 3-4 seconds, then returns. It is very annoying.

Screen temperatures below (right - normal, left - drawdown fps).



Put a new, clean OS, did not help. According to the previous owner he had no such problems (and to not believe him makes no sense because I got it for free).

Computer clean. Not a speck of dust. I just took apart the PSU and vacuumed/wiped everything. What could be the problem? Help a teapot, please.

(PC configuration)
Percents i5-4570 3.2 GHz
Card - Gigabyte GeForce Gtx 760
PSU - Chieftec aps-750CB
Cooler - CoolerMaster Hyper 212X