Toumani Diagouraga marked his first start for Leeds with a rare goal as Steve Evans' side beat Championship rivals Bolton 2-1 to reach the FA Cup fifth round.
Souleymane Doukara put Leeds in front early on but, after bossing much of the match, Leeds were forced into some late desperate defending.
Wanderers captain Darren Pratley netted for a fourth time in six games to pull a goal back before top scorer Gary Madine hit the post four minutes from time.
But That proved as close as Bolton got much to the delight of nearly 7,000 Leeds fans inside the Macron Stadium.
Doukara shot the visitors in front after nine minutes with a helping hand from Wanderers keeper Ben Amos.
And Frenchman Diagouraga netted his first goal since moving from Griffin Park six minutes from half-time to double Leeds' advantage.
In fact, it was Diagouraga's first goal since finding the net for Brentford in March 2013.
After beating Eastleigh in a third-round replay and MK Dons last weekend more was expected of a Bolton outfit lining up with only one recognised striker in Madine.
The sides drew 1-1 at the Macron Stadium last October with Mirco Antenucci's penalty cancelling out one of two goals by Shola Ameobi during his three-month stay with the Trotters.
Diacouraga followed his goal with an early second-half caution for bringing down Preston target Liam Feeney but Leeds remained on top.
Giuseppe Bellusci came forward from the back to take a free-kick nearly 40 yards out that had Amos anxiously pushing the ball over the top of his crossbar.
Lennon tried to change Wanderers' fortunes after 67 minutes taking off Arsenal loanee, Wellington Silva and Mark Davies for Kalyne Woolery and Jay Spearing
Madine then shot shot straight at Marco Silvestri after 70 minutes in a rare home attack.
Scott Wootton joined the attack to fire high from a good position as Leeds sought a third goal to kill the tie.
Skipper Pratley then saw a goal-bound effort blocked by Bellusci at the expense of a corner but the captain came up with his latest goal 10 minutes from time to give the Trotters' hope.
Madine then struck the woodwork with Leeds rattled but the visitors held on to seal a spot in Sunday's draw.