Lag in singleplayer

1. When I create a map, after 10 seconds is start to lag( block lag, nofall damage or map not generate good)
2. When I close the game and restart minecraft and select singleplayer map, MC is give me CRASH!
3. I have a good PC to play Minecraft and I not have problems with the computer
3. Multiplayer is good, no lag but please help me to fix this singplayer lag !
4. Oh and this problem is valid in all minecraft versions, like 1.8