Continuity mistake: When Kelly is at the grill, right after being called a "dullard" by Bud, Kelly grabs Bud's wrist with her left hand. As we pan out on the exact same scene, her hand is nowhere near his wrist.
Factual error: Al uses ashes to cook food on the grill. You can't just throw ashes in a grill and light them! They wouldn't light at all. That's like trying to light cigarette ashes and expecting them to burn hot enough to cook food.
Answer: It was one of the hoses connected to the engine, nothing specific, but to indicate that Al tampered with the vehicle.