When Mac discovers that his belt is too short to reach from the sink faucet to the electrical box, the cover to the box is already unfastened, but then when Mac is ready to tuck the end of his belt into the box, he unscrews the cover with his belt-buckle.
When Mac sees the smoke alarm for the first time, its test button is on the top. In the following scenes, the button is on the bottom.
A 12 volt car battery could not cause a television picture tube to explode, but sparks could ignite hydrogen gas produced by the battery causing the battery itself to explode.
At the end MacGyver gets the antidote with only about two minutes left before he is supposed to die. But the antidote is a pill, which would mean it would take at least thirty minutes before it would be digested and take effect. However, as the hit man puts it, MacGyver "starts to die" at the six hour mark. He clearly explains that the antidote must be taken within 6 hours to be effective, not that MacGyver is to die at the end of the six hours.
Mac, with Lisa, unreels a fire hose across a hallway through a doorway and out a window to make the men looking for them think they left the building. The hose stretches across the hall at the level of Mac's lower chest. After the men enter the room and fall for the deception, they leave and turn left down the clear hallway, Mac and Lisa come out of hiding, leave the room and turn right down the hallway and continue as if nothing is in the way. They should have had to duck under the still stretched out fire hose.