Herbie Goes to Monte Carlo (1977)

Race car driver, Jim Douglas goes to Monte Carlo to enter his car, Herbie, in the Monte Carlo rally. When they get there, Herbie falls for another driver's car and Jim falls for the driver Diane, who thinks he's weird. But what they don't know is that a pair of thieves who stole a very valuable diamond, hid it in Herbie's gas tank. And the thieves try to get it back.