I know very little about cars. So what kind of massive problem might come on like that without any previous symptoms? The character is pretty car-savvy, and I would prefer it to be something that he could diagnose based on the sounds the thing's making and what he sees under the hood. But if it has to be mysterious, that's all right too. Just want to make sure whatever I choose is plausible.
At the moment I have his carburetor going out. *shrug*