England, an unbeatable 2-0 up in the series, were 27 without loss off eight overs after Pakistan captain Inzamam-ul-Haq won the toss and elected to field on Thursday.
Marcus Trescothick was four not out and England captain Andrew Strauss, the more fluent of the two left-handers, 22 not out.
Only two balls from Mohammad Asif were possible before rain forced the players off the field for 34 minutes.
When they returned Asif, playing his first Test of the series after an elbow injury, had a strong appeal for lbw with the fourth ball of the over against Trescothick although replays suggested the ball might have gone over the top of the stumps.
Asif, in for the dropped Mohammad Sami, then saw Strauss leg-glance him for four.
While Trescothick struggled to find his touch, Strauss had no such problems. He leg-glanced Asif for four, cover-drove Umar Gul to the boundary and then drove Asif down the ground.
At lunch Asif's four overs had cost 13 runs and Umar Gul's four, 14 runs.
This was England's first Test series win anywhere since last year's Ashes success at home to Australia and their first at home against Pakistan since 1982.
England were unchanged from the side that won the third Test at Headingley by 167 runs but Pakistan made three changes in all.
Mohammad Hafeez, playing his first match of the series after his recent call-up, and Imran Farhat, fit again after a finger injury, replaced dropped opening batsmen Salman Butt and Taufeeq Umar, who've both left the tour.
This meant Pakistan had their fourth different opening partnership in as many Tests.
Hafeez, 25, was playing his first Test since September 2003, when he made the last of three apperances against Bangladesh.
Pakistan, as they had been all series, were once again without spearhead fast bowler Shoaib Akhtar as the 'Rawalpindi Express' continued his recovery from a left ankle injury.
The umpires hoped to restart play at 1.30pm local time (1230GMT), provided there was no further rain.