I have a 99 Pontiac Bonneville the problem I am having is their is a knocking noise when I drive and when I stop it makes a popping noise. please help
Read the "Service Issues" on the Pontiac V-6 here: http://www.underhoodservice.com/servicing-gm-s-3800-v6-engines/ The sounds you described remind me of a worn timing belt/jump timing, but it could be caused by many things. I would get a mechanic to check the engine timing, then move through other possible causes like a dead coil pack, gasket leak, ECU problem, etc.
It doesn't have the check engine light on
Could be poor/bad gasoline causing knocking and detonation, but I would still have it looked at even if check engine light is not on.
Looking for a Used Bonneville in your area?
CarGurus has 540 nationwide Bonneville listings starting at $1,899.
Search Pontiac Bonneville Questions
Pontiac Bonneville Experts