On the left corner of the box, he turned Vale defender Steve Rowland to hammer his 27th goal of the season for City with a low shot into the far corner on 14 minutes.
The England Under-21 striker had a short game though as with half an hour gone he went down holding his left leg.
There was a double change as one of the referee's assistants had to be replaced at the same time after sustaining a hamstring injury.
After a fortnight off in which other results fell for them, City knew a win would revive their play-off bid.
But their tactics were strangely sterile - a succession of high balls down the middle which the Port Vale defence comfortably dealt with.
And Vale were equally negative with former City striker Lee Matthews their solitary striker with occasional support from leading scorer Billy Paynter.
On a sunny day both sides produced football from the deep freezer, although it improved slightly as both managers were forced to reflect on their tactics at half time.
City had been content to let Vale come on to them and this was almost fatal when Levi Reid was allowed space and time for two long shots.
Steve Phillips turned the first away comfortably for a corner but had to make a more serious dive to keep the other out of his top right-hand corner.
There was increasing pressure on the home defence but on 68 minutes it all came right for City.
On the right wing Scott Murray's speed had seen Craig James and Danny Sonner already booked for mis-timed tackles, but this time he sped past two challenges to get in a low cross which was turned in by Lita's replacement Paul Heffernan.
It wasn't the cleanest of volleys but it squirmed over the line to rescue an unhappy afternoon for the former Notts County striker.