I once had a car with a fast food tick - for years and it never amounted to a problem. The car sounded fine normally, it sounded fine standing over the engine with the hood open, but put me up against a brick wall at a fast food drive through and there was a consistent tick. My solution was to eventually stop worring about it. It never got any worse and the car always drove fine. The ticking never showed up under any other circumstances. I concluded it was a twilight zone thing. Of course one solution is to stop eating fast food.