If that's the case (him being excited), what worked for Buddy was to take him in the car all the time (not less). If I was running to the store for milk, I'd take them, and all sorts of other meaningless errands and Bud soon figured out the car wasn't always so damn exciting!! If the only place you ever take him in the car is somewhere that he is terribly excited to go, then of course he will be excited to be in the car, you need to make it a menial task (in my humble opinion).