Just to be clear, this is a 2D game, right?
My guess is that you have something in your code that is slowing down the process. You didn't list your computer specs, but I assume you have a decent rig.
I would look at each subroutine / function to see how long it takes them to run in the game. You can store the perftimer() value prior to accessing a subroutine / function and then read the perftimer() again after the subroutine / function ends. You calculate the elapsed time and then print that value on the screen. Then you look at what is taking so long to process. You might want to collect, say, 10 elapsed time values and average them so that you don't constantly have a different number showing up on-screen. Anyway, this might point you to where the slowdown is occurring.
If that doesn't show anything, perhaps you could post the code you are using to move / display your map.
So many games to code.....so little time.