The central bank sold $39.6 million to banks with a cut-off price of 6.9512 pounds to the dollar, unchanged from the last auction on Monday.
The bank had offered to sell $40 million. On the black market, the dollar was traded for 7.33/7.35 pounds on Wednesday, having stayed within a range between 7.30 and 7.35 since last week.
The pound has been under pressure during three years of political turmoil.
Foreign currency reserves were around $17 billion in January, down from $36 billion before the uprising that led to president Hosni Mubarak's downfall in 2011.
The central bank introduced dollar currency sales over a year ago. Last month, it held a $1.5 billion exceptional auction, its largest ever, to restock the market with dollars and curb unofficial currency trading.