Close Encounters of the Bird Kind - S2-E20
Continuity mistake: When Dick Butkus is in the clubhouse doing "The Butkus Group", the door is open. After Max and Abby leave and Bill Nye says you can't charge a cell phone with a potato, it's still open. But in the outside shot of Max Abby, the door is now closed.
Answer: Walkers are attracted to noise, they can tell who's dead and who isn't dead, in S1 when Rick and Glenn cover themselves in walkers' guts they're able to get far by walking through the herd of walkers because they smell like they're dead, but as soon as the guts get washed off by the rain the walkers immediately attack them, if you draw attention to yourself they will attack you which we've seen that many times throughout the series that it's not always successful. Whether you're covered in guts hiding under dead corpses or under a car.