I had a gingival graft and it's been 3 wks and I have a bad smell from the site. Is this normal?

Bad smell/ bad taste from the gingival graft site is not notmal you should have the site evaluated to rule out infection. You will need antibiotic to clear this infection meanwhile,you should continue rinsing with chlorhexidine mouth wash yo keep area clean 

Gum grafting involves the placement of either the patients own tissue or tissue bank tissue at the recipient site.  Sometimes part of the graft material may not survive and this can result in a necrotic or bad smell.  I would expect however that the wound should be well on its way to healing at 3 weeks so I suggest that you check back in with your surgeon and have them evaluate the cause.