Lilly fanned 11 in six innings to get his third straight win and Soriano had his second leadoff homer in as many nights.
"I don't think I just stand out there and try to throw fastballs by guys," said Lilly, who has consecutive double-digit strikeout games for the first time in his career.
"I have to mix my pitches and change speeds and locate the ball and things like that," he said. "And at times, when I got my curveball going, I'm going to get some strikeouts on it. But I'm not going to say I'm a power pitcher."
Backed by three RBIs apiece from Soriano and Geovany Soto, who also homered, Lilly (4-4) allowed four runs and six hits in six innings. After striking out 10 against Arizona in his previous start, he fanned eight in the first four innings. He left after throwing 102 pitches on a 46-degree night.
Cubs pitchers combined to strike out 15 against the Padres, whose 308 strikeouts are second in the major leagues behind Florida's 326.
Soriano, who has three homers in as many games, is 10-for-19 over the last five games after a slow start that included a trip to the disabled list. He also had a key two-run single in the second inning after a wild pitch by Jake Peavy on a third strike to Lilly allowed the pitcher to reach. The single gave the Cubs a 3-0 lead.
"I feel great. I'm swinging the bat really well," said Soriano, who was booed early in the 10-game homestand. "That's part of the game. It motivates me to try to make myself a better player."
Peavy (4-3) needed 87 pitches to make it through four innings. He gave up four runs and seven hits, struck out eight and walked two.
The wild pitch was costly.
"It would have been a different game. I still had the chance to make some pitches to Soriano there," Peavy said. "I'd much rather get Ted Lilly out there than have to face Soriano, but I didn't. I have to make better pitches. I'm obviously just frustrated. I have to do better than that. Having to get pulled after four is embarrassing."
Manager Bud Black said Peavy's pitch count got high in a short amount of time. He decided to pinch-hit for his standout starter in the fifth with two on
"Jake's stuff was OK. The slider was effective. You saw that he had eight strikeouts. The fastball command was probably not Jake-like," Black said. "It doesn't happen often. I think over the last couple of years, he has the most quality starts of anybody. This guy is one of the best pitchers in the game, so it's a rare occurrence."
Soto's RBI single in the third made it 4-0, but San Diego closed within a run in the fifth on Tadahito Iguchi's two-run single and Lilly's wild pitch.
Soto's seventh homer, a two-run drive off Wilfredo Ledezma, put Chicago up 6-3 in the fifth. Khalil Greene's sacrifice fly cut the margin, but Aramis Ramirez had an RBI double in the sixth and Johnson a run-scoring double an inning later off Bryan Corney to make it 8-4.
It was Peavy's shortest outing since going four innings against Arizona last Sept. 5. ... Soriano has 46 career leadoff homers, third in major league history behind Rickey Henderson (81) and Craig Biggio (53). He has homered in three straight games. ... Peavy made a nice diving catch of Soriano's pop in the fourth. ... Lilly has 12 double-digit strikeout games overall.