Abdullah showed his worth in the 44th minute, when he reacted well to save Kim Cheol-ho's powerful shot from inside the area.
Seongnam centre-back Cho Byung-kuk had a good chance 10 minutes into the second half, but could only scuff his volley straight at Abdullah from 12 yards out.
Shabab were increasingly coming into the game and Jung had to pull off two great saves in the 64th minute to deny the visitors.
Nassir Al Shamrani finally burst into life when the Saudi Arabia striker intercepted a Seongnam pass and cut in from the left before powering a low right-foot shot that was parried by a diving Jung.
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Dzenan Radoncic of Seongnam headed the ball during the game. |
The big keeper then responded instantly to save the follow-up by Abdullah Shuhail, using his left knee to deny a close-range shot by the left-back.
Seongnam winger Song Ho-young came on for Cho in the 66th minute and five minutes later the 22-year-old intercepted a pass outside the Shabab area, but with only Abdullah to beat, he tamely poked the ball into the keeper's legs.
Eight minutes later, Song blasted over wildly when picked out at the top of the area by Molina as Seongnam sought a decisive second goal.
Shabab pressed on for the equaliser and Saudi Arabia midfielder Abdoh Autef and striker Fisal Bin Sultan were both brought on in the last 10 minutes, hoping to repeat the decisive impact they made as substitutes to win the first leg.
However, it was Brazilian playmaker Marcelo Camacho who came closest with a snap-shot from outside the area, although Jung comfortably tipped over the effort.
Driven on by a fired-up Ognenovski, who played in the 2008 final for Adelaide United, Seongnam held out to continue their excellent record in the AFC Champions League.
The club reached the semis three years ago, losing on penalties to eventual champions Urawa Reds, and reached the final in 2004, when they lost to Jeddah giants Al Ittihad over two legs.
Ilhwa beat Al Nassr of Saudi Arabia 1-0 in the final of the 1995 Asian Club Championship when Shin was a player and the 40-year-old Seongnam legend will now aim to also win as a coach.
This year's one-leg final will be held at the National Stadium in Tokyo on November 13, when Seongnam will look to succeed fellow K-League giants Pohang Steelers as champions.