I recently test drove a fairly low milage (under 60K) 2010 A5 manual and it started up fine, pulled out ok, but when i put any load on it at all it would break up/miss badly in any gear. Like a violent car shaking miss. I drove it probably 5-10 miles, under various conditions,. trying to get it to 'clear itself out" and drive properly, but every time i accellerated it would miss. In neutral the car would rev freely with no miss. The odd part is there was no "check engine" light on the dash...Needless to say I didn't bring it home, but the used car dealer said he was going to take it to the local audi dealership to have it looked at, and if the fix was minor he would get it fixed and call me. I'm curious what it may be? Coil pack? spark plugs? bad wire? old/low octane fuel from sitting? What would cause such a miss yet not trigger a light on the dash?