Substitute striker Dario Cvitanich saved Pachuca from ignominy with two goals in the final eight minutes to give the CONCACAF champions a 2-2 draw. There was no extra time.
The Argentine pulled one back with a close-range volley and equalised when he stepped over a low cross and surprised goalkeeper Adel al-Hosani by backheeling it into the net a minute from time.
Al-Wahda's Brazilian midfielder Hugo was asked to take the opening penalty in the shootout again after Pachuca captain Miguel Calero moved well off his line to save it. Hugo netted from the second attempt.
Calero, however, saved al-Wahda's third penalty from captain Abdulraheem Jumaa and Modibi Diarra blasted his over the bar to hand victory to the Mexican side.
Midfielder Ismaeil Matar had put the UAE champions ahead just before halftime when he volleyed home a cross from the left.
Al-Wahda had central defender Hamdan al-Kamali sent off for a foul on Colombian striker Franco Arizala in the box but Paraguay's Edgar Benitez blasted the penalty over the bar.
The home side made the most of the let-off and Mahmood al-Hammadi scored a fine solo goal in the 77th minute. His first effort was parried by Calero at close quarters but the rebound fell kindly to him and he slotted the ball in from a tight angle.
