Thanks for asking the query,
Sour taste in the saliva can be due to abscess
formation it can be because of many reasons , gingivitis
inflammation of the gingiva
due to plague
and calculus deposition ,
Periodontal abscesses formed due to decayed tooth, Depositions on the tongue due to poor oral hygiene .
Visit to the Dentist
and get checkup done .
Get complete mouth scaling polishing and root planing done .
Maintain a good oral hygiene , use lukewarm saline gargles 3-4 times a day , use antiseptic mouthwash gargles twice daily . Avoid eating hot and spicy foods.
Take vitamin suplements .
Hope this helps out .