The Spaniard entered the weekend with a two-shot advantage after a pair of bogey-free 64s and was still without a blemish as he turned in 32 to lead by five.
Some ragged swings set in on the back nine but he came home in level par despite making his first two bogeys of the week and will head into round four at 18 under, four clear of English duo Joe Dean and Ross Fisher, Frenchman Romain Langasque and Dane Niklas Norgaard.
Elvira's only DP World Tour win to date came three years ago at Celtic Manor when he needed a playoff despite taking a six-shot lead into the last 18 holes.
He was hoping to use that experience in Antwerp.
"I was leading by six then, I'm leading by four (today)," he said.
"I could have taken three or four more just to be relaxed but this game is funny sometimes.
"I cannot hit it as good as I want and be leading by four, it's just a weird game.
"I learned a lot about being patient that day so hopefully I can take that into tomorrow."
Tied for second, Dean was a supermarket delivery driver the week before he finished second at the Magical Kenya Open in March but revealed this week he has given up the day job.
A 66 on Saturday, including two chip-ins, put him in contention for a life-changing win.
Melbourne's David Micheluzzi carded five birdies on his way to a 68, putting him in a tie for 37th at seven-under overall.
Fellow Australian Jason Scrivener (69) is a shot further back in joint 44th.
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