Recall most advice given here in the past relates to ensuring a slight delay between switching on ignition and actually starting the engine. This gives time for ecu to sort itself out. Suggest a delay until fuel primimg sound stops, speedo has jiggled around (as it does if you watch closely) and settled to zero and immobiliser light gone out. Sounds a lot but only a few seconds in practice.
I was told this by the Ford Regional Service Manager, when I had a recurring problem on a new Fiesta, a few years ago.
He advised me to wait until all the check lights had gone out, before starting the engine.
It solved the problems on the Fiesta and it is now habit for me on my 4/4 and my current tintop.
