Other mistake: Al's and Peggy's birthdates are around 1948/1950, respectively. Supposedly, Al married Peggy after she got pregnant the day of his 4 touchdowns in high school in 1966. How could Kelly have been born in 1971?
Other mistake: Depending on the season the Bundys' address is 9764 Jeopardy Lane. Season 4 the address is 9674. But in the opening credits when Steve is shown on his porch the address is 9674. (00:00:20)
Answer: It was one of the hoses connected to the engine, nothing specific, but to indicate that Al tampered with the vehicle.