When Steve is fighting Omega's men, he pushes one aside with his left, non-bionic arm, producing a bionic thud.
Steve tells the lady that she had a loose battery contact, but if this was the case, the engine would not have turned over.
Steve tells the lady that it sounds as if the power isn't getting to the starter, yet the engine cranks just fine. The correct analysis would be that the power wasn't getting to the ignition wires.
Rudy speaks of "fuel cells burning hydrogen while extracting breathable oxygen from the water", but this would be impossible because the hydrogen's combustion would consume most or all of whatever oxygen was produced.
Rudy speaks of bubbles of hydrogen being wasted as they rise to the surface of the water, yet no bubbles are visible as Steve swims underwater. Lee Majors (or his stunt double) is clearly just holding his breath.
The sound of the hot chick's small hatchback car starting up is very noticeably different from when she was cranking it a moment before; it has the much deeper-toned, "heavier" sound of a higher-volume-displacement engine being turned over and running, and so it's obviously a recording of a much larger vehicle being started.
Oscar and Rudy say the breathing device will not work because of a lack of power source. But since Steve's bionic arm will power the device, a backpack no larger than Steve's bionic arm would do the job. They would still have a self sufficient breathing device.
The merc who is posing as a maintenance painter says "over" after each of the two identical radio transmissions that he makes back-to-back. He would know not to repeat himself in that way, since it could cause the radio listener to "stomp" on his transmission after his first message, and also cause him not to hear if the listener responded.