Good day gents, I bought an Accord EX-L 2.4 about 5 months ago and ive just noticed some engine ping. It happens after accelerating from a stop, but goes away once im up to speed. I cant hear it in the cab, but only when im next to a wall with the windows down. I live in central Nevada, the elevation is 4000ft, and i have run a full tank of 91 oct to try to solve it with no progress. Im taking it to the dealer soon, but is this common amongst other owners? What would cause it? Thanks for the help!

Chris