Shadab Khan celebrates after scoring half century during the third ODI match at the Multan International Cricket Stadium on Sunday. AFP
Pooran turned his arm over only for the second time in his 43-match ODI career to take 4-48 after Pakistan slumped from 85 without loss to 117-5, having won the toss and opted to bat.
The innings seemed to have fallen apart with Babar Azam's rare failure for one but Shadab wielded his bat to the best effect.
Between a 60-minute dust storm that curtailed the match to 48 overs-a-side, Shadab hit three sixes and four boundaries off 78 balls before being bowled in the last over. He improved upon his 54 against New Zealand in Wellington in 2018.
Imam-ul Haq avoids a ball during the third ODI match at the Multan Cricket Stadium on Sunday. AP
Sensing the Multan stadium pitch helping spin, Pooran brought himself up after Fakhar Zaman (35) and Imam-ul Haq (62) gave Pakistan a solid start.
Pooran chipped in with the wickets of Zaman, Haq, Mohammad Rizwan (11) and Mohammad Haris (nought) off just 25 balls, having never taken more than one wicket in his first class career.
Haq smashed seven boundaries and a six off 68 balls for his 14th ODI half century. He became only the second batter to score seven or more fifties in successive ODIs.
Former Pakistan great Javed Miandad, celebrating his 65th birthday on Sunday, held the record for most fifties in successive ODIs with nine, scored in 1987.
In between Pooran's destruction, Azam fell leg-before to spinner Hayden Walsh for just one, having hit a century and 77 in the first two matches.
Shadab added 84 with Khushdil Shah (34) for the sixth wicket and 40 for the eighth with Mohammad Wasim who made six.
Pakistan, leading the series 2-0, handed fast bowler Shahnawaz Dahani his ODI debut and brought back Hasan Ali, resting Shaheen Shah Afridi and Haris Rauf.
West Indies left out Alzarri Joseph, Anderson Phillip and Brandon King to bring in Keacy Carty, Jayden Seales and Keemo Paul.