Battlefield 3 gtx 660ti Lag

BRAMnl

Honorable
Sep 30, 2012
1
0
10,510
Hi all,

My problem is i have a Gtx 660 ti.
When i am playing a game like bf3 i can play for like 10 minutes without lag.
My FPS is then like 120 wel i begin but after like 10-15 minutes it starts with lagging to a FPS of 40.
And it is lagging like going back to 120 and after a few minutes it goes back to 40 and it repeats al the time.

Could somebody plz help me :??:

Bram