Loud noise at low idle only

Tapping noise may be a failed lash adjuster, sometimes they will come good if they are just sticky with gum and carbon, first try adding a quality engine flush (read and understand instruction on flush)and do a filter and oil change, if this does not help you will have to replace the failed adjuster, also do an oil pressure test as well, test cold idle, hot idle and hot 1500rpm, post readings for evaluation.