I had bought an original QTR MD-08A IR sensor. After making appropriate connection and pushing through code to extract position values from IR sensor I am getting fluctuating values from even a stationary position of my bot.
The QTR MD-08A IR sensor has a specified sensing range. Make sure that the distance between the sensor and the object is within the specified range. If the object is too close or too far from the sensor, the readings may be inaccurate.Infrared sensors can be affected by ambient light in the environment. Make sure that the environment where the sensor is being used has consistent lighting conditions, and that there are no other sources of infrared light that could be interfering with the readings.
While the sensors were calibrating, did you make sure each one was exposed to both the brightest and darkest portion of the surface it is sensing?
It looks like the fluctuations you are seeing are pretty small, and could be caused by environmental factors (i.e. a nearby window, shadows, fluorescent lights). You might try making a quick sheath out of something like electrical tape to help shield the sensor and see if that helps at all.