Ibrahimovic has made an immediate impact in California since his arrival from Premier League giant United, scoring twice in his match-winning debut against neighbour Los Angeles FC last month.

The 36-year-old Swede continued his inspired form for the Galaxy on Sunday (AEST), scoring the winner in the first half at a sold-out Toyota Park in Chicago.

After Ola Kamara had two goals ruled out for offside in the opening stages of the match, Ibrahimovic broke the deadlock on the stroke of half-time when he headed Ashley Cole's cross past Fire goalkeeper Richard Sanchez.

"I think the game was difficult, it was not an easy game especially with the weather." Ibrahimovic said. "I mean, we come with the sun, they come with the wind, but the sun was the stronger today, so we’re happy."

It moved Galaxy up to second in the Western Conference, while Schweinsteiger — another former United player — and his Fire have only won one of their opening five games to languish second from bottom in the Eastern Conference.

Fire is only a point better off than reigning MLS champion Toronto, which suffered a 2-0 defeat against Colorado Rapids.

Toronto reached the CONCACAF Champions League final during the week after upstaging seven-time winner America.

Head coach Greg Vanney prioritised the first leg against Guadalajara by resting the likes of stars Sebastian Giovinco and Jozy Altidore against the Rapids, who took full advantage thanks to goals from Jack Prince and Shkelzen Gashi.

FC Dallas remains undefeated in the league after a 1-0 win over New England Revolution, Portland Timbers claimed a wild 3-2 victory against Minnesota United, New York Red Bulls accounted for Montreal Impact 3-1, 10-man DC United trumped Columbus Crew 1-0, while San Jose Earthquakes and Houston Dynamo played out a 2-2 draw.