Despite moving the tee times up due to the threat of bad weather and sending the field off at the first and 10th holes, little more than an hour's play was possible before an approaching storm halted the action.
Lee Westwood birdied the first from 32 feet to improve from 27th to 18th and alongside Tiger Woods, who parred the same hole, on one under par.
McIlroy, needing to win to dethrone Luke Donald, was 11 under and two ahead of Americans Harris English and Tom Gillis.
Padraig Harrington had a bogey and a birdie in the first four holes and so was level par and 34th.
Play was expected to resume at 11.30am local time after a delay of 111 minutes. That would mean McIlroy starting just under an hour later.
Westwood made another move forward on the resumption, holing from over 50 feet for eagle at the third. He was up to 10th, but still seven strokes adrift of McIlroy.
Woods then eagled the hole as well, in his case from 27 feet, to rejoin Westwood on four under, but of more concern to McIlroy was that Justin Rose birdied the first from the same distance and improved to eight under.
McIlroy's advantage was immediately cut in half when he finally made it onto the course. He missed a 10-foot chance and Gillis made no mistake from seven.
Woods, meanwhile, sank a nine-footer on the short fifth and was up to ninth place on five under, six behind.
McIlroy parred the first five holes, but that included holing from 13 feet at the second and eight feet on the fifth as the pressure built.
His lead had gone back to two when Gillis bogeyed the second, but the 43-year-old birdied the next and was only one behind again.
Rose also bogeyed the second to be four back in joint third spot, while Woods and Westwood both reached the turn in 31 to be five and six back respectively.