The most frequent culprit behind a 45 FPS lock is how the game manages refresh rates and vertical synchronization. Disable V-Sync and Match Refresh Rates
Getting stuck at 45 FPS in Modern Warfare 3 is a common but solvable problem. Start with the core fixes: update your drivers, disable V-Sync, and set the game to fullscreen. Then, methodically move through the advanced tweaks. You'll likely find the solution that fits your specific PC setup along the way. cod mw3 45 fps fix