bad sensor?

Hi everybody... Big problem. 2k spectra GSX has starting problem when it is cold out. the car is getting fuel and spark, but will not start. It did the same thing last winter and the dealer changed the following things with no luck. Spark plugs and wires (twice), ignition coils, fuel pump, o2 sensor. The vehicle runs excellent when it is above freezing, but does not start in the cold. Any advise would be helpful, thank you all in advance, and Merry Christmas!!

bigger battery. stock ones were terrible