2008 Honda Civic Pings with Acceleration and A/C on

My car has been pinging for the 9 of 10 months of owning it. Dealer suggested changing gas station to Chevron when I already fill with Chevron. I traveled in 4 states and used different gas - still no change. I also tried premium for a month and didn't make a difference.Dealer is still persisting on it being a fuel issue - no codes turn on alarming them of an issue. Also told me there is nothing wrong with the timing belt (computer doesn't say so). They are trying to "research" now after I told them to drive a different 2008 Civic on the lot which didn't ping. Please help! I thought Hondas were quality cars!