[Belovan]

It is not likely that not having a wait timer would cause the robot to not stop moving, but they are good to have. Also, before you enter the while loop you should reset the gyro, so that moving the robot around before you run the code won't make it go more or less than 90 degrees. Another thing you should check is to see if turning in the direction you are telling the robot to turn in gives you a negative angle, like -90 degrees.