it could be as simple as tire rod ends are wearing out, if the guy you bought it from messed with anything in the front of the car and tightened the tire rods too tight (the thing that connects to the front sway bar) then that can produce a clicking noise. i doubt its pinging, i mean honestly that is a pretty serious thing, you know when an engine pings, not hearing that is like not knowing you have a flat tire. if it started out small and is now louder it has to be wearing. it could very well be something in the rear as suggested. have you checked the lug nuts. you could be hearing shearing if a lug nut is not tightened all the way. however usually if that is happening you don't hear it accelerating (usually). its obviously something in the suspension. if you do not hear it while the car is idling in neutral in the driveway, then its not in the engine. valves can make a clicking noise but nothing substantial, injectors in the winter can be noisey as well but that again is a slight sound and can be heard from outside the car parked. check the bushings on the tirerods, those could be getting warped, if you don't know what to look for, take it to a mechanic. Last hting you want to do is find out its a stupid lug nut thats not tightened all the way and then while driving along you shear off the a couple lugstuds and your wheel falls off. thats a bad look, beleive me, i know from experience.
