Citroen Xsara Picasso engine management light on

Engine runs rough no power, light on , fuel to go reading increases as you drive reachs 1242 then stops, changed fuel pump and filter. worse in this hot weather seem to heat sink after stopping after driving then trying to restart, some times after getting up speed turn off engine ,coast , then restart if lucky will run ok but not lately tried another petrol station but added cleaner to fuel. every thing wlse works OK had it scanned Changed engine speed senor but problen returned in this heat. any clues