The standard remedy for pinging is switching to high octane.

Seriously, it could be spokes, loose skewer, computer magnet hitting the sensor, etc. It's hard to say from the small amount of information you provide. Since you mentioned a difficulty keeping the front wheel true, I assume you are truing it yourself. I'll say that either there is somrthing wrong with the wheel, or you are an ultra-perfectionist. Front wheels just don't need truing very often.

After truing the wheel, stress-relieve the spokes by grabbing a pair of parallel spokes in each hand and squeezing as hard as you can for a few seconds. Don't worry - you won't break anything! Wear gloves if you want. That should take care of the truing problem.