The bank offered $40 million and said it had sold $38.4 million at a cut-off price of 7.1401 pounds to the dollar, a rate unchanged from its last sale on Monday.
The rates at which banks are allowed to trade dollars are determined by the results of central bank sales, giving the bank effective control over official exchange rates.
In the unofficial market, the pound was trading at about 7.70 to the dollar on Wednesday, also unchanged from the previous day, one trader said.
The price of dollars on the unofficial market been largely steady since the government announced late last week that it would hold a weekly Sunday auction in addition to the sales it already holds on Monday, Wednesday and Thursday.
The bank did not give a specific reason for adding the sale, but the central bank governor said last month he would take measures to calm the parallel market in the Egyptian pound, which has grown in recent weeks.