Daniel Carcillo also scored for the Flyers, who had slipped to eighth place in the Eastern Conference with a 1-6-1 stretch over their previous eight games. Brian Boucher made 31 saves for Philadelphia.
Despite goals from Dan Cleary, Darren Helm and Pavel Datsyuk, the Red Wings lost in regulation for the first time in 13 games. The defeat clinched the Central Division title for the Chicago Blackhawks.
Chris Osgood, making his first start in goal since Jan. 27, had 21 saves for Detroit.
In a game that had significant playoff implications for both teams, the Flyers got off to a sizzling start.
Carcillo opened the scoring just 17 seconds into the game with his 12th goal of the season. Following a turnover in the neutral zone, he skated in and snapped a wrister that went off Osgood's glove and into the net.
Timonen made it 2-0 seven minutes later, but the Red Wings answered with a pair of goals in a three-minute stretch. Cleary deposited a loose puck in front of the net for his 14th goal before Helm tied it on a rebound for his 11th.
Giroux gave the Flyers a 3-2 lead just 53 seconds into the second period, blasting a loose puck past Osgood. It was Giroux's 15th goal of the season, but his first in 14 games.
Asham made it 4-2 late in the second period, redirecting a pass from Timonen past a helpless Osgood.
Datsyuk scored his 27th goal early in the third period, but Detroit could not get the equalizer past Boucher.
NOTES: The Red Wings have not won in Philadelphia since Jan. 25, 1997, a stretch of six games. ... Jimmy Howard's streak of 25 consecutive games started was the longest by a Red Wings goaltender since Tim Cheveldae started 29 in a row in 1991-92. ... With two assists, Flyers RW Ian Laperriere notched his first multipoint game since Jan. 12. Timonen recorded his first multipoint effort since Dec. 14. ... Carcillo had missed the previous two games due to a suspension for high-sticking the Devils' David Clarkson on March 28. ... The Red Wings killed off all three Flyers power plays and have now allowed just three goals in their last 45 short-handed opportunities.
