Every morning when I start the cold engine of my old Honda, especially in the winter, the car started hesitantly and I can smell the unburnt gas. Tokeep the engine running, I have to keep pressing the gas pedal until rpm can itself sustain at 2k to 3k. When this car is new, the process took about two minutes and I don't need to press the gas pedal, now it takes five minutes or longer in cold days. The car acts normal after the five minutes of my morning blue is over. Also, the emission is somewhat blackish in that first five minutes. The emission turns to normal white steam after the rpm hits 3k then drops to normal 1k instantly. Does anyone know what causes the problem, and is it expensive to fix? Thanks.