Vauxhall Vectra no power engine mangment light comes on and off......

when the eng man lamp comes on the car goes into limp home mode to avoid damage to the engine.it may be a minor fault. get the ecu memory read at any good garage most have code readers and will quote you on what they find.no power is not a problem,and will go when the eng man lamp problem is fixed

Could be your mass air flow meter which fastens onto the air box & regulates the air that goes into the engine. Had this problem with my Vectra a couple of years ago, a check on your main dealer computer should tell you exactly what it is though.