Thanks for the responses. The sink and shower water are fine and have zero odor. Momentum I am not sure how to answer your question. The toilet has a large handle that flushes and a small one recessed into the large one. The small one just fills the toilet with water. The strange thing is that the smell is sometimes immediate when simply filling the bowl prior to use.
Rock Dodger any idea how to determine is the vent is clogged. I'm not sure where to begin looking.
Thanks for the info and help folks. Please keep the suggestions coming.