Jermaine McSporran shocked promotion chasing City with a 72nd minute equaliser in front of a crowd of more than 12,000 at Ashton Gate.
The striker capitalised on excellent work by Danny Bulman, who beat Louis Carey near the right corner flag before producing an inch-perfect cross to be nodded home at the near post.
The goal rewarded a backs to the wall effort by Wycombe, who had to repel constant pressure from promotion-chasing City.
It looked as though the home side would claim the points when Brian Tinnion's introduction from the subs' bench paid quick dividends.
The veteran playmaker went on for Luke Wilkshire on 56 minutes and three minutes later provided the pass for Marc Goodfellow to volley home from a narrow angle.
For all their dominance, City forced few testing saves from Steve Williams as Wycombe's defence, superbly marshalled by Stuart Nethercott dug in with great determination.
But the visitors managed only one other worthwhile goal attempt when McSporran's 24th minute shot was deflected wide but they will have been by far the happier with the outcome.
Both sides had to make first half substitutions, City defender Matthew Hill who had passed a late fitness test on a calf injury never looked comfortable and gave way to Clayton Fortune after 21 minutes.
Young Wycombe winger Matt Bloomfield took a knock in the early stages and hobbled off to be replaced by Ian Simpemba on 38 minutes.
City will rue their lack of finishing power on a night when promotion rivals Plymouth Argyle and Queens Park Rangers both won.
For Wycombe draws are barely enough in their current position but Adams must have drawn great encouragement from the resilience shown by his bottom of the table team.