That first quarter was the Cavaliers biggest in nearly two years.
Behind 15 points from Ilgauskas and eight from Carlos Boozer, Cleveland bolted to a 39-28 lead. The 39 points were the most in a period for the Cavaiers since they totaled 42 in the fourth quarter against the Los Angeles Lakers on March 26, 2002.
The Cavaiers preserved the early advantage through three quarters, but a 7-0 run early in the fourth quarter gave the Bucks an 83-81 advantage.
The game remained tight with just over four minutes remaining.
Ilgauskas finished with 29 points for Cleveland, which has won seven of nine. James had 24 points, 10 assists, seven rebounds and four steals and Boozer recorded his 28th double-double with 22 points and 13 rebounds.