Substitute Michael Kightly returned from injury to spare Wolves' blushes and prevent Cambridge from an FA Cup third-round shock at Molineux, inspiring a 2-1 win over the Blue Square Premier side.
Cambridge were on course for another giantkilling after taking a shock half-time lead, Scott Rendell firing United, who reached the quarter-finals of the competition in 1990 and 1991, in front from the penalty spot after 42 minutes.
Wolves defender Neill Collins was penalised for handball and Rendell made no mistake from the spot to grab his 14th goal of the season.
But nine minutes after stepping off the bench, Kightly - whose absence with an ankle injury has coincided with Wanderers' worst form of the season - levelled from 12 yards before setting up Collins for the winner with just two minutes remaining.
Cambridge, who beat Wolves 1-0 at Molineux 17 years ago, nearly made the worst possible start.
Darron Gibson and Matthew Jarvis linked up well and the ball eventually found Jay Boothroyd, whose effort was superbly charged down by Mark Albrighton inside the first 40 seconds.
Wolves - without a win in seven games - have struggled for goals in the Championship this season, netting only 24 times in 26 games, but they came close again in the 14th minute, Gibson's drive being well saved by visiting goalkeeper Danny Potter.
With more than 4,000 fans backing their team, Cambridge - sitting fifth in the Blue Square Premier - nearly took the lead in the 24th minute.
Mark Convery, with just one goal this season, was denied by a decent save by Wolves goalkeeper Wayne Hennessey.
The home side went up the other end and came close again, only for Potter to deny Stephen Ward from 20 yards.
With the crowd starting to show their frustration, only a stunning save from Potter kept the scores level.
Gibson swung over a free-kick which was met by Stephen Ward, but Potter produced a magnificent block, with Andy Keogh heading the rebound wide.
Gibson and Ward both fired wide as the home side searched for the opener prior to half-time before Rendell struck.
Wolves manager Mick McCarthy threw on Freddy Eastwood for Keogh at the break and the early stages of the second half saw the home side dominate.
Ward and Eastwood both went close, but McCarthy's dismay was evident on the touchline.
Wolves went close again in the 57th minute when Ward fired over the crossbar from Jarvis' corner
Kightly replaced Ward on the hour and nine minutes later he hauled Wolves level, claiming his first goal since October from 12 yards from Jarvis' cross.
With a replay at The Abbey looming, Collins made amends for his handball by heading home the winner to break Cambridge hearts.