Re: You have to believe first, then you'll get your evidence.
While I fully agree that the argument you're trying to refute is nonsensical, I'm not sure a car analogy is the most effective way to do it. A theist would probably respond by saying that through the grace of God you receive a loan (Bad credit? No credit? No problem! Just tithe 20% of your income for the rest of your life!).
The theist is expressing the view that you can make sufficiently convincing evidence appear by believing until it does (I've personally been told that I have to "fake it until you make it"). The amount of belief "required" is not objective and can't be predicted by anyone else, because it's at God's discretion based on His plan for you.
Potentially effective rebuttals at this point depend on the theist and your own familiarity with the subject matter. You can bring up delusional behavior if you want to go with psychology. You can bring up Mother Teresa's letters where she no longer believed and was told that meant she was God's instrument. You can bring up the "if you meet the Buddha in the road, kill him" argument against false enlightenment. Or the foolhardiness of trying to please a whimsical god.
However, I'm of the opinion that your efforts would be better spent in trying to steer the conversation towards something along the lines of the subjectivity of these experiences means that they are highly personal and that we should not make objective rules based on them. Jdog 22:47, 15 July 2011 (CDT)