Poppy's By the Tree (1) - S2-E1
Continuity mistake: Bud asks to go down to the high school "tomorrow" to meet the man who met Andy Griffith. Earlier Al reads the events page in newspaper. The event was said to be "tonight."
Poppy's By the Tree (1) - S2-E1
Continuity mistake: When Kelly walks over to the table, she burps. She breaks character by laughing with her head down yet a second later, she has a serious look on her face.
Answer: It was one of the hoses connected to the engine, nothing specific, but to indicate that Al tampered with the vehicle.