Plot contrivance: Cars' universe features all range of human technology used by sentient cars. They have Gatling guns, tasers, radars, remote bombs, electro-magnets, GPS, satellite TV, holograms......but no sonars, that's too high-tech.
The lack of a sonar on the villain's ship in the opening sequence makes it possible for Finn McMissile to escape even though most if not all modern ships have sonars. He should have at least been detected.
Plot contrivance: Holley Shiftwell is a spy-car that can transform into a plane. She obviously decides to use her unique ability in the final chase sequence of the movie instead of using it in all other danger situations where a flying vehicle would have solved everything a lot quicker. Good job ! Logic loses again !
Unaddressed Issue: If the Scooby-Dooesque villain Miles Axelrod was a fake eco-friendly electric car using conventional gas to run, how come no one noticed the smell of the burned fuel ? Or see heavy smoke come out of his exhaust pipe ? Or that the sound his motor emitted was the same as everyone else ? Wait, do cars smell in this movie ? If they can taste, they probably smell too. Wow, this entry is longer than it should have been. This is depressing.
Trying to find plot holes in a movie about talking cars. Where is my joint? Ok. Great. Wait. Why is this the first Pixar movie that sucks? Can Disney's greed ever be satisfied? But greed wasn't invented by Disney (so I've heard), isn't it part of human nature? Does that mean hating on the movie on its greedy roots is also an attack on humanity itself? Boy that movie is deep. I just want some Cheetos. Yeah, Cheetos, that would be nice. I wonder if they talk too. They don't have sonars, I'm betting $5 on it. Wait no, I take it back, don't touch my money.