If you are trying to add up 100 readings to get some sort of average, then
(a) after you add up 100 readings, you need to divide by 100
(b) make sure you don't overflow the int
try seeing what the actual readings are, without confusing yourself and me with the stoopid map() function.
try reading the y and z axes as well, that will give you a better idea if the device is actually working and the
communications to the device are actually working.
the answer from an accelerometer is going to look rather boring unless the device is actually accelerating.