“Little Miss Sunshine” is a collision between a road comedy and a dysfunctional family that would be better off apart. The arguments are loud and the comedy is dark, but it has enough disarming, inspired moments to make up for its lack of sunny characters.

Six dreary lives in Albuquerque are temporarily put on hold so that the Hoover family can pile into a yellow Volkswagen bus as temperamental as its passengers. Their destination: California, where daughter Olive (Abigail Breslin) can compete in a preteen beauty contest called “Little Miss Sunshine.” If she wins, maybe the whole family will feel as though it’s escaped its persistent bad luck.

Olive is the sole family member young enough not to have developed a slew of self-destructive behaviors and off-putting tendencies. The rest of the family’s bad habits are set in stone. Mom Sheryl (Toni Collette) can’t stop smoking. Dad Richard (Greg Kinnear) is a motivational speaker who has invested all of his dreams, and much of the family’s nest egg, in a failing self-promotional campaign. Their son (Paul Dano) is deep into his teenage years, and has retreated from the world by refusing to speak. The grandfather (Alan Arkin) is a profane, porn-loving crank who always speaks what’s on his bitter mind. And Sheryl’s brother, Frank (Steve Carell), is suicidal.

Arguments erupt over the dinner table frequently, as no one bothers to be polite. Screenwriter Michael Arndt and co-directors Valerie Faris and Jonathan Dayton play these bits for big laughs, letting the dark comedy accumulate. Where the film gets into trouble is when that comedy cedes to sentiment. We stop laughing with the family because suddenly we’re laughing at them.

This wild, unpredictable tone is a problem, but it is not fatal. Despite a clumsy finale and a few other scenes that are overdramatic, the characters are played with utter sincerity, and the screenplay has plenty of insights about winners and losers. No one likes to suffer, the film assures us, but suffering is essential; by playing around with this theme, showing the contrasts between the miserable have-nots and the vapid have-plentys, “Little Miss Sunshine” earns its laughs and praise.

(Running time: 101 minutes. Rated R: language, drug use, sexual content)