Well there is a simple technique to know if the IR you get is wrong or not..
using a micro controller, you have to establish 2 readings, store them, and compare them,
1- send IR, and read the sensor output, store it
2- Stop sending IR,and read the sensor output, store it
if you get (1) from the sensor in both cases, then the IR is not working good, dure to surrounding light, noize, etc...
if you get (1) then (0), there is an abstacle detected.
if you get (0) in both cases, there is nothing infront of you, for SURE!
think about it..