Weinke relieved Delhomme, who was knocked out of the game when he slid and was crushed by safety Kenoy Kennedy.
"I knew right when he got hit that he was going to be dazed," Weinke said. "I didn't have time to think about it. I had been standing around all day. I just had to get loose. I was excited.
"You never want to see someone go down, but I've been waiting for this opportunity for three years."
The backup quarterback took over at midfield with 2:56 left and showed remarkable poise.
Weinke connected with Proehl on a third-and-3 from Detroit's 41 and threw the TD pass to the second-string receiver one play after Proehl dropped the ball in the end zone. Weinke completed 5 of 7 passes for 47 yards and threw his first TD pass since his rookie year.
The 2000 Heisman Trophy winner started 15 games for the Panthers in 2001 and threw for 2,931 yards, trailing only Peyton Manning's rookie record, and was a seldom-used backup the next year.
The past two-plus seasons, he hadn't taken a snap.
"You don't really know if you're ready until you get the opportunity," Weinke said. "But I felt as comfortable as I've ever felt playing quarterback in this league."
The Lions (2-3) got the ball back at midfield with 24 seconds left but couldn't complete a pass. On their previous possession, a first down might've sealed the victory.
"I didn't like the way we finished the game," Detroit coach Steve Mariucci said. "We played hard, but when we needed a first down up six, or needed a stop, we couldn't get it."
Safety Mike Minter made a play that allowed Carolina (4-2) to win its third consecutive game.
Marcus Pollard caught a pass from Joey Harrington and was caught by Minter, stopping an 86-yard gain at Carolina's 5. The Lions had to settle for Jason Hanson's 25-yard field goal and a 20-14 lead with 5:08 left.
"If I didn't catch him from behind, we wouldn't have had an opportunity to win," Minter said. "That definitely ranks up there for me with the big plays I've made."
The Lions returned two interceptions for scores in the first half and Hanson made two field goals in the second half.
Delhomme and Harrington had three turnovers apiece early in the third quarter. With Carolina receiver Keary Colbert's fumble and Detroit receiver Mike Williams' fumble, the teams combined for eight turnovers through three quarters.
"It was a game like no other," Carolina coach John Fox said. "Our defense did a great job keeping us in the game. We hung around and luckily, offensively we were able to come out with that last drive."
Delhomme was 15-of-25 for 236 yards with two TDs and three interceptions. Fox said Delhomme was "shaken up" by Kennedy's hit, which drew a penalty.
Harrington, who was booed constantly, finished 17-of-28 for 201 yards with an interception and two fumbles.
"To boo Joey here, that's tough on him and tough on all of us," Pollard said. "At the same time, I can sympathize with the fans, too."
Pollard had three catches for 105 yards, but came up short on a reception that would have put the Lions ahead by two scores late in the game.
"That is one that I have to get in," he said.
"Usually, the best defense wins. Today, the luckiest defense won," Panthers defensive tackle Brentson Buckner said. "Their defense played better than ours."
It was tied at 14 at halftime after both teams blocked a field goal.
Detroit's offense finally scored with 40 seconds left in the third quarter, taking a 17-14 lead on Hanson's 52-yard kick.
- The Lions were without receiver Roy Williams (quadriceps) and defensive end James Hall (groin) while Carolina running back DeShaun Foster (knee), cornerback Chris Gamble (ankle) and fullback Brad Hoover (shoulder) were also inactive.
- Carolina's Julius Peppers had one sack, his first of the season.
- The Lions returned two interceptions for scores for the first time since 1976.