checked compressions when cold all good, gave a run round block and misfire seemed to come and go, rechecked compressions no3 slightly down on the rest so kev was right ecu shutting down, i rechecked no 3 injector feed and live ok and earth switching so looks like could be head off dont know whether to forte flush and gas treatment as the car is a auto and only done 50,000 miles driven by an old lady could be sticky valves or rings ?