The world No 2 played an eight-hole stretch around the turn in eight under par, but the two late errors saw him sign for a four-under 68 and fall three behind midway pacesetter Graeme Storm.
Storm equalled the course record at Glendower GC, with a blemish-free 63 lifting him two clear of Jbe Kruger, Peter Uihlein and overnight leader Trevor Fisher Jnr.
McIlroy is one of five players sitting a further stroke back in a share of fifth spot, with 48 players still to complete their rounds when play was suspended due to the threat of lightning.
