Ngongotaha held a slim 2-1 lead at half time before going on to take the match 4-3, in another thrilling match.
Defender Dave Haua was the hero for Ngongy with two goals, while captain Josh O'Sullivan and Dane Willemsen also netted for the club.
At Neil Hunt Park in Rotorua, United got off to a slow start and went a goal down early. Then Rangers scored a controversial penalty just before half time to take a 2-0 lead into the break.
After the break, Brad Hill earned another controversial penalty for United but captain Lawrie Scott banged his shot over the cross bar.
Rangers capitalised on the mistake with a nicely taken free kick. South Auckland defender Atunesh Prasad slammed home the 25m shot to make it 3-0.
It was not until the last 20 minutes that the home crowd finally had something to cheer about.
New signing Moha Al-Harby scored a free kick for United which fizzed into the top corner. United then showed plenty of spirit to score two more quick goals and tie the match.
The first came from the boot of Hill and the second off the head of substitute Nathan Tina.
However, Rangers broke away in the dying minutes and Akshay Shandil put his shot past goalkeeper Andrew Gibbs to secure the win.
Rotorua coach Rich Barter said when his team managed to pull it back to 3-3, he was confident they would go on and win the match.
"I was thinking there is only one team going to win this. It was just an absolute one-way onslaught."
He said it was disappointing to go on and lose from there but "that is football".
"That is as much excitement as you can get from a game of football," he said. "For the crowd that came to watch it, there was a real buzz around the ground."
Barter said his team played well, especially during the second half, but a couple of things really hurt them.
"Unforced errors was number one and number two was the first 20 minutes."
