City has just one win in eight games on the road — the type of form that contributes to Manuel Pellegrini's side being three points behind leader Leicester.West Ham remained sixth, six points behind Tottenham, which occupies the fourth Champions League place. The east London club is enjoying its best run in the league in 19 years in its final season at Upton Park before moving to the nearby Olympic Stadium.
Both times Aguero canceled out goals from Enner Valencia, who put West Ham ahead only 53 seconds into the game after Cheikhou Kouyate swept past Yaya Toure before cutting the ball back to the winger.
Aguero hit back from the penalty spot in the ninth minute after Carl Jenkinson tripped David Silva.
A superb save by Joe Hart prevented West Ham going in front, with the goalkeeper flinging his body in the air to turn over Dimitri Payet's free kick.
"That save did feel good ... I had to move my feet quickly," Hart said.
Hart was beaten again 11 minutes into the second half. Michail Antonio launched a quick, long throw-in to the penalty area, Valencia got in front of Nicolas Otamendi and knocked the ball past Hart.
"We were not very concentrated," Pellegrini said. "Maybe with the throw-in you are thinking that there can be a danger. But we knew before the game that Antonio has a very long throw-in."
But Aguero played a one-two with Kelechi Iheanacho before slotting the ball past Adrian into the bottom corner with nine minutes to go.
"It's very important for him (Aguero) to be 100 percent fit," Pellegrini said. "I hope he will continue like us until the end of the season."
West Ham could have won it with the final touch of the game, but Cheikhou Kouyate's header hit the crossbar.
"We could have got the third goal even though they were dominating," West Ham manager Slaven Bilic said. "So when I went back into dressing room I felt disappointed. But that's good — that shows how well we played."
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