Sharp IR distance sensor outputting consistently high voltage
If your power supply is indeed the issue, then add a simple low pass filter in your power supply connections as close to the sensor as possible. I'd start with the following configuration to see if it improves the situation. Double check if Vcc at the sensor is 4V5 - 7V. 







simulate this circuit &ndash; Schematic created using CircuitLab

Assuming that the device is powered by Arduino's 5V and assuming that the device is drawing 30mA of current, the voltage accros R1 will be 0.3V and the supply voltage for the sensor will be 4.7V, sufficient according to the datasheet. R1 and C1/C2 form a simple low pass filter that will suppress high frequency noise from the power supply.

Keep wires as short as possible, keep them as close together as possible. If possible twist the wires for the power supply and twist the wires (V(out) and GND) for the output.