my fusion starts normal from cold and runs normal until the engine heats up .after getting to normal running temp it starts to sort of misfire at low revs or when pulling off from a stationary position but once at high revs it seems ok when idling it feels very rough and of course the engine light comes on .tried changing the coil pack for a new one . the car ran better for a longer period about 10 miles but then its back to being sluggish. so back to square one .checked leads and they look fine. so if ignition system is not at fault including ecu .could it be down to oil pump/water pump/ thermostat failure.can any of these parts cause the same symptoms?
please help. this is driving me mad
big thanks in advance