Iowa fell to 4-5 and 2-3.
IU, which trailed 14-0 at one point, remains in contention for a bowl berth and a spot in the Big Ten title game if it wins out by beating Wisconsin, Penn State and Purdue.
Coffman, who started and then was benched for most of the first half, threw for three touchdowns and more than 300 yards. That’s a first for an IU quarterback since Ben Chappell did it against Purdue in 2010.
Receivers Kofi Hughes and Cody Latimer both had more than 100 receiving yards. Latimer caught three touchdown passes.
Lightning delayed the kickoff about 75 minutes.
Iowa scored first when James Vandenberg hit Kevonte Martiin-Manley with a 24-yard TD pass for a 7-0 lead midway through the first quarter.
IU quarterback Nate Sudfeld, who took over on the team’s second possession, had thrown 65 passes without an interception. His 66th was intercepted by cornerback Christian Kirksey and returned 18 yards for a touchdown. That made it 14-0.
Sudfeld stayed in the game, kept his poise and led IU down the field. The drive ended on Mitch Ewald’s 45-yard field goal.
Early in the second quarter the Hoosiers passed on another Ewald field goal on fourth and half a yard on the Iowa 8-yard line. Rather than use the 6-5 Sudfeld on a quarterback sneak, Houston got the ball and was stuffed for a loss of four yards.
The Hoosiers blew another scoring chance on their next possession when Ewald missed a 38-yard field goal attempt.
IU got the ball one more time before halftime, and Wilson went back to Coffman. He passed the Hoosiers to a touchdown, the last 15 yards on a pass to Cody Latimer, for a 14-10 halftime score.
Iowa came out strong to start the third quarter, forcing the Hoosiers to punt and then driving into the red zone. But cornerback Antonio Marshall intercepted an under-thrown pass in the end zone to stop that scoring threat.
Coffman hit Kofi Hughes with a 77-yard pass to set up a 6-yard touchdown pass to Latimer. Iowa responded with an 88-yard TD drive to go ahead 21-17 with 12:17 left.
Isaiah Roundtree’s 39-yard kickoff return setup IU at its 39-yard line. Coffman the drove IU down the field before hitting Latimer with the 30-yard game winner.