Continuity mistake: Marcy says her parents never let her have a Barbie as a child. In Season 2 episode 14, Guys and Dolls, Al and Steve steal Marcy's Barbie from the basement to sell to buy a new baseball card.
Continuity mistake: Marcy's niece asks Bud to take a shower so she can get out of her sticky clothes. Next scene, she's sitting on the couch with a towel on her head. She talks to Bud awhile then gets up and leaves. Shes wearing the same "sticky" clothes and she takes the towel off her head, and her hair is completely dry.
Answer: It was one of the hoses connected to the engine, nothing specific, but to indicate that Al tampered with the vehicle.