When Steaua Bucharest levelled up Juan Mata's first-half goal just before in the interval, Chelsea were facing an uphill task to keep our European campaign alive, but an attacking display with plenty of chances created in the second half yielded the goals needed - John Terry scoring from a set-piece and then Fernando Torres netting the vital third.
Torres then missed a late penalty, keeping the tension high against opposition with their own cutting edge. Petr Cech made saves in each half but we go through to the quarter-finals.
John Mikel Obi and Eden Hazard, impressive in the second half at Old Trafford, were given starts in place of Frank Lampard and Victor Moses. John Terry returned to partner David Luiz in central defence and cup-tied Demba Ba was replaced by Fernando Torres.
Steaua were unchanged from the first leg.
With the visitors leading 1-0 after the first meeting, the tie was set up for one of those gripping and nail-biting nights of European football, and so it proved. Chelsea showed early penetration down our right flank. One swift move found Mata who switched play to the left where Hazard's touch left the ball slightly behind him and the chance to shoot was missed. Mikel, following up, had his own effort blocked on the edge of the area.
For all Chelsea's initial possession it was Steaua who had the first proper chance and Chelsea had once again reason to be grateful to Cech. Mikel had the ball pinched from him and suddenly Rusescu was away behind a chasing defence. His shot was a good height for the Chelsea keeper who was able to deflect it wide of the far post. There were 12 minutes played and an away goal had been avoided.
The Steaua skipper Bourceanu was not too far away from the top corner of Cech's net with an ambitious effort soon after.
Cech had to deal with another shot before the Blues rallied and worked the Steaua keeper for the first time midway through the half. There was some fabulous play from Hazard under pressure out on the right in the build-up and when Mata crossed, the chance fell to Mikel. His shot was low, well-hit and on-target but Tatarusanu got down to push it wide.
The keeper had less luck on 33 minutes when Mata drew the tie level with a shot that hit Tatarusanu but still went in. Oscar and David Luiz had worked to win the ball on halfway and send Mata forward. He fed Ramires who made a penetrating run through the middle before returning the ball to Mata. Showing clever footwork, the Spaniard moved it on to his right for the finish. 1-0.
Chelsea v Steaua Bucharest
Chelsea looked to quickly follow up the goal. Torres shot powerfully wide before Hazard, who was causing Steaua all sorts of problems with his ability to ride challenges, tested the keeper who beat a stinging shot out.
Just before the interval it needed an important recovery tackle from Cole deep inside the Chelsea area to prevent Popa having a go at goal, after the Chelsea left-back and David Luiz had let the winger escape much further up the pitch.
The Blues had been in the ascendency but that Steaua attack was a warning shot. On the stroke of half-time, the corner that followed was initially blocked by Torres with Cech keeping out a follow-up shot, but he could do nothing when defender Chiriches fired high into the net from close range.
Chelsea needed at least two more goals, just as we had at the start of the second period in the previous match at Old Trafford. Bourceanu sliced down Mata on the halfway line to earn the game's first booking.
Rapa followed into the book for taking down Hazard out wide but 10 minutes had passed between those cautions without a Chelsea chance.
Mata remedied that from the free-kick for the foul when he found the head of John Terry, who scored with one of his classic near-post headers. Now the requirement was one goal with just over half an hour to play.
Chelsea v Steaua Bucharest
Steaua were looking increasingly ragged in defence as the Blues pressed them back but still we couldn't keep our back door secured. Cech had to save a dangerous shot from Chipciu.
Torres put Chelsea back ahead in the tie with 70 minutes played, finishing from inside the area with his left foot across the keeper, after Hazard flicked on Mata's pass. It was a clean and clinical move and we were now leading 3-1 on the night.
Moments later there was a strong claim for penalty for a foul on Torres as he turned back inside Szukala whose sliding challenge clipped the Chelsea striker. The official behind the by-line was close by but still the decision didn't come. The same defender's boot then inadvertently gave a prone Torres a nosebleed.
We needed the insurance of more goals. This tie was still on a knife edge. Oscar and Torres both went close.
On 85 minutes we were finally awarded a penalty, and there was no debate as Bourceanu clumsily hacked at the shin of Hazard, the night's outstanding attacker. With no Frank Lampard on the pitch there were a few candidates to take it but Torres stepped up. His second goal of the night proved elusive as he fired high onto the crossbar, a miss that thankfully didn't prove costly.
It was Chelsea who went closest to a stoppage-time goal with Mikel having another shot blocked and substitute Yossi Benayoun narrowly failing to apply the finish when Torres fired across the face of goal.
Chelsea (4-2-3-1): Cech; Azpilicueta, Terry (c), David Luiz, Cole; Ramires, Mikel; Oscar, Mata (Moses 90), Hazard (Benayoun 90+3); Torres.
Unused subs Turnbull, Ferreira, Cahill, Bertrand, Lampard.
Scorers Mata 33, Terry 58, Torres 71.
Booked Mikel 69, Cole 80.
Steaua (4-2-3-1): Tatarusanu; Rapa (Adi Sobrinho 83), Szukala, Chiriches, Latovlevici; Pintilii, Bourceanu (c); Popa, Chipciu, Tanase (Tatu 78); Rusescu.
Unused subs Stanca (GK), Gardos, Filip, Prepelita, Iancu.
Scorer Chiriches 45.
Booked Bourceanu 49, Rapa 57.
Referee Stéphane Lannoy from France.