The returning Ricky Holmes had given Northampton an early lead in a battle between two teams with promotion aspirations and the visitors were further boosted when Joe Riley was sent off just after half-time.
Bury, however, not only got on level terms thanks to Etuhu but won the game in dramatic circumstances when El-Abd headed home in the dying stages.
For home boss David Flitcroft the game showed the 'charater' he feels his side has got while opposite number Chris Wilder also had praise for the home side.
He told the official NTFC website: "The sending off galvanised them and the reaction from Bury was that of a promotion winning team."