The Little Engine That Could hits the rails again in “Turbo,” except that in the new 3D kidflick from DreamWorks Animation, it’s a snail that has the big dream and a NASCAR track he has his protruding eye on. The picture is colorful and amiable enough, but like a car race that drags on for hundreds of laps, it grows repetitive and more than a bit dull before the finish line is reached. It also has several problems that undermine its message and narrative drive.

When we first meet Theo (voiced by Ryan Reynolds), the little critter is just one of dozens of snails “working,” assembly-line fashion, a tomato patch in a suburban garden, where they’re regularly terrorized by a nasty little boy on a tricycle. Unlike his fellows, who contentedly go about their daily routine under the foremanship of his practically-minded brother Chet (Paul Giamatti), Theo is obsessed with the idea of racing in NSCAR, spending his evenings watching the races on TV and listening to perpetual champion Guy Gagne (Bill Hader) encourage his fans to go for the gold, however difficult the road might seem. Still, Theo’s dream seems impossible, until he’s endowed with super-speed after an accidental encounter with a street racer.

That’s the first problem with “Turbo”—the moniker Theo is eventually given because of his newfound ability. His success isn’t based on grit and determination; it’s literally the result of a chemical reaction, not unlike Peter Parker being zapped by a radioactive spider. He’s no longer the Little Engine That Could—he’s a high-speed locomotive, which seriously alters the moral of the tale. And though a twist in the final race ultimately throws him back on his own “natural” resources, it’s too little, too late.

Anyway, one big dreamer apparently wasn’t enough for the screenwriters—another problem—because they add a second in the person of Tito (Michael Pena), a taco-truck driver always looking for ways to turn the little stand he runs with his more pragmatic brother Angelo (Luiz Guzman) into a success. When he discovers Theo/Turbo’s amazing speed, he enlists the other colorful business owners in their run-down neighborhood (Michelle Rodriguez, Richard Jenkins and Ken Jeong) to chip in to cover the sponsorship cost of the mollusk’s entrance in the Indy 500. Soon they’re all off to Indiana in the taco truck, along with the reluctant Chet and the humans’ other racing snails (Samuel L. Jackson, Snoop Dog, Maya Rudolph, Ben Schwartz and Michael Patrick Bell).

There are, of course, some objections to the snail’s acceptance among the competitors—after all, despite his name, Turbo’s no car. But after Guy speaks up on his behalf, he’s admitted to the race. It’s only at this point that villainy enters the picture in a form you might anticipate it you find foreign accents suspicious. But that’s also too little, too late, although the scripters are smart enough to force Turbo to finish the race on his own power rather than his extraordinary swiftness.

The animation is fine and the use of 3D not as oppressive as it often is (the expert cinematographer Wally Pfister served as a visual consultant, and it shows), while the voice talent adds some sonic luster even if Reynolds is a pretty bland hero. (Henry Jackman’s score, which often falls back on hip-hop to jazz up the action, is, on the other hand, mostly an annoyance.)

Very young children will probably be most receptive to “Turbo,” appreciating its color and story simplicity. But while older kids and adults may get a few chuckles from the secondary characters (a running gag with Bell, playing a chubby snail who calls himself The White Shadow, is amusing), they’ll probably that the movie’s running on fumes long before the final lap.