Watched by their best opening-day crowd for three decades, they twice snatched the lead, but twice Queens Park Rangers struck back within seconds.
The second time they did so - in injury time - with a header from centre-back, Damion Stewart, after a desperate free-kick, was a killer for City manager, Gary Johnson.
He had gambled in the dying minutes on pulling off his £1million buy Lee Trundle for the fresh legs of veteran Scott Murray.
It looked like a winning bet when Murray, shooting on the spin, ripped a shot into the far top corner.
But the message from this busy match was clear; both sides have to tighten up in defence.
Rangers expected to come under early pressure from the Championship new boys, but did so in a bizarre manner as Mike Mancienne so nearly presented them with an own goal.
Lee Camp rescued him with an athletic leap to his left, but then took part of the blame for the Lee Johnson goal which beat him in the 33rd minute.
The shot, after Johnson had raced through in a supporting role, went across him and rolled in off the far post.
Inside 30 seconds, though, the inquest in the QPR camp had turned to celebration as a John Curtis high throughball from inside his own half caught City cold.
Their keeper Adriano Basso had to race out, but came off worse as he collided with Rangers Dexter Blackstock. He was flat out on his face as Blackstock knocked his goal in.
There was a long hold-up while Basso was treated and, in the second half, he was replaced by new signing Steve Henderson.
Henderson made two fine saves, but was also lucky as shots from Martin Rowlands twice hit his woodwork.