Penalties and turnovers frustrated Iowa State at times, but the Cyclones still had enough to overpower their FCS opponent and start 3-0 for the second straight year and sixth time since 1981. Four of the five previous 3-0 starts led to bowl appearances.
Jantz completed 19 of 26 passes for 209 yards, with touchdown throws of 16 and 5 yards to Chris Young and 22 yards to Aaron Horne. He was intercepted once and lost a fumble.
Western Illinois (2-1) trailed 31-0 before Pat Smith kicked a 26-yard field goal in the first minute of the fourth quarter. Iowa State was playing its second-team defense by then.
While never in danger during the game, Iowa State still has a lot to clean up before its Big 12 opener against Texas Tech on Sept. 29. The Cyclones were penalized seven times for 75 yards and were minus-three in turnovers - two interceptions and a fumble.
The Cyclones have time to get that work done because they're off next weekend.
Western Illinois started the season with victories over Butler, a non-scholarship FCS program, and Division II Indianapolis. But an opponent from a BCS conference simply was too much for the outmanned Leathernecks.
Their only chance was Iowa State suffering a major letdown after its 9-6 victory over Iowa, the Cyclones' first win in Iowa City in 10 years, but that didn't happen, even if ISU wasn't especially sharp.
It looked as though a major rout was in the offing when Iowa State jumped to a 14-0 lead in the first 5 1/2 minutes on White's TD, the longest run of the season for the Cyclones, and Jantz's 16-yard pass to Young. The Cyclones then stalled repeatedly and most of the damage was self-inflicted: a fumble by Jantz and an interception, then two personal fouls and three holding penalties.
But the defense and Kirby Van Der Kamp's punting kept Western Illinois in check. Van Der Kamp pinned Western at its own 8, 1 and 16 with his three first-half punts and the Leathernecks never drove farther than the Iowa State 44 until late in the third quarter.
The second holding penalty against the Cyclones nullified Aaron Horne's 61-yard punt return for a touchdown with less than 2 minutes left in the first half. But the offense regrouped and Jantz completed four passes to Young for 55 yards, the last covering 5 yards for a touchdown that made it 21-0.
Young finished with a career-high seven catches for 86 yards, matching his reception total for the first two games. He caught only six passes last year.
Jantz's touchdown pass to Horne, a perfect strike down the middle of the field, made it 28-0 early in the third quarter. Edwin Arceo tacked on a 49-yard field goal to make it 31-0, enabling coach Paul Rhoads to get his second-teamers into the game.
Iowa State jumped on the Leathernecks early, just as expected. On the fifth play of the game, White took a handoff, burst through a big hole in the middle of the line, cut to his right and outran the pursuit to the end zone, helped by Young's downfield block.
Before that 56-yard burst, Iowa State's longest run this season had been 20 yards by Jantz.
After the ISU defense forced a quick three-and-out, Horne returned a punt 48 yards to the Western Illinois 18. Three plays later, Young caught a pass from Jantz at the 10, turned and sprinted to the end zone to make it 14-0 with 9:34 left in the quarter.
Western Illinois managed only 81 yards in the first half and 178 for the game. The Leathernecks' Nikko Watson gained 76 yards in 17 carries, while Josh Hudson completed 9 of 18 passes for 73 yards. He was sacked twice and hurried on several other throws.