England 234 (Morgan 48, Sodhi 3-53, Boult 2-47) beat New Zealand 230 for 8 (Williamson 112*, Munro 49, Ali 3-36) by 4 runs
Williamson: England held on to win a thrilling third one-day international by four runs, despite a classy century from New Zealand captain Kane Williamson.
On a difficult surface, England battled to 235, a total that looked plenty when the hosts slipped from 80-1 to 103-6.
Williamson added 96 with Mitchell Santner and reached 100 in the 49th over, leaving 15 to get from the 50th.
He hit Chris Woakes' third ball for six but could not find the required six from the final delivery in Wellington.
England go 2-1 up and can seal the series in Dunedin on Wednesday.
Victory on Tuesday would give England their fifth successive ODI series success as they build towards the 2019 World Cup on home soil.
That World Cup ambition seemed particularly pertinent in Wellington, a ground where England suffered their must crushing defeat in the 2015 tournament, a nine-wicket loss to New Zealand.
On this occasion, England returned unrecognisable from the side beaten in a day-night match that was completed before the floodlights were turned on.
Whereas victory in the second ODI in Tauranga was an all-round demolition of the Black Caps, this was a streetwise and intelligent adaptation in tricky conditions, even if they were almost denied by the brilliant Williamson.