A motor vehicle exhaust aftertreatment system includes an exhaust conduit that includes a NO.sub.x adsorber, a particulate filter, a reformer for generating reformate containing hydrogen and carbon monoxide from a fuel source, a reformate conduit, and an oxygen sensor. In response to a pressure drop through the particulate filter attaining a threshold value, reformate is introduced under selected controlled flow conditions into the exhaust conduit and caused to undergo combustion. The resulting exotherm maintains the temperature within the particulate filter within a selected range that is effective to cause oxidation and removal of soot from the particulate filter. Introduction of reformate into the exhaust conduit is discontinued when the pressure drop through the particulate filter is decreased to a selected value.