For a pup -- stick with it. They usually grow out of it. My Shay barfed often when young and his equilibrium kicked in and he grew up loving car travel. Crating with towels you can pull out and replace, not feeding before travel, allowing windows down some and vents blowing also helps a lot.
If it continues -- it's likely anxiety. My sheltie is horrible. She will throw up. She drools so bad we travel with a rain slicker on her. Rescue remedy, ginger, Benaryl, no help. She starts drooling if we head towards the car. The only thing I haven't tried that people suggest is a Thunder Shirt. She had a bad former life (puppy mill breeder) and she was taken to a groomers for nails & shaving or to the vet. Nothing else. It's really sad to watch. She loves being places for training, outtings, visiting family. She just hates getting there. It's really a challenge to return from training since treats are given and the tummy is not empty. We haven't thrown up in the last 6 trips and I count that a major triumph.
Don't stop taking the pup. Keep at it so he outgrows it. Take him lots of fun places so that the car means going someplace happy (not just the vet's and grooming and boarding and such).
Cara -- Central CA
+ Shay -- GSD
+Melody Rose & Cubby Shelties