Fiesta 1.6 TDCi will not run properly until warmed up to 80 Degrees

Ford Fiesta 1.6 TDCI engine  2016 that will not run properly until it has fully warmed up to 80° C.

The engine starts OK so that would  indicate it is not the glow plugs, if I try and take the engine RPM to say 2500 and hold it in that position when the car is stationary, after a few seconds the engine splutters.  Sometimes the engine speed increases momentarily then dies altogether and comes back again then dies  comes back,  sometimes it just cuts out altogether, it  is impossible to drive as the car has no power.  It will run OK ticking over.

Once the engine has warmed up, everything seems fine and the car drives normally.  At the moment before any journey I have to warm  the engine up for 10 minutes so I can drive,  is not just annoying  for me and the neighbours.

Things I’ve tried so far-

1)   Coupled up to an OBDII Reader and no fault codes are showing,  when I looked at a graph of the fuel rail pressure when the engine blips and judders  there is a momentary spike in the fuel pressure reading and it seems to rise and then fall rapidly.

2)   Replaced the FUEL PUMP REGULATOR METERING VALVE – no difference

3)   Replaced the fuel filter – no difference

4)   Thought it could be the EGR valve sticking,  so I banked it off, -  this has not fixed the problem but the card does seem to have more power when it is warmed up.

5)   Fitted A few all nine primer bulb in an effort to ensure no bubbles were in the fuel line – this is still not fixed the problem.

Has anyone any ideas what part of the car could be causing this temperature related behaviour.

Could it be the fuel rail sensor  that is faulty.

Thanks for any help