My dog keeps throwing his food up?

He's 13 and recently he's been throwing up his food, he lost half his teeth when he was about 8 because he kept chasing and biting car tires. I was thinking that he's not chewing his food properly and thats why? We're taking him to the vets soon but I just wanted some other opinions. He also has decided to take his food bit by bit out of his bowl indoor and takes it outside to eat.