hello
This fault only occurs sometimes: mostly it starts and runs fine.
* I start the engine, it fires normal, then after 4 or 5 seconds the engine splutters and will stall out...

I have worked out a resolve to get going....
when/if it begins to splutter, I quickly increase the revs a little.... this gives me time to quickly CLICK CLICK with the ignition key... (turn the ignition OFF then ON again)... the engine THEN is firing with no spluttering and doesnt stall out. It can then be driven as usual.

It has occurred first thing in morning (cold), it has occurred on a restart (hot).
Just recently it has started to occur whilst driving!... usually (but not everytime) when trying to pull away again after decelerating as at a junction.
A quick OFF/ON with the ignition... and the engine immediately is running ok again.

CAR INFO
my car is a Y REG, Mondeo Estate XL, petrol 1.8 ( replaced recently to a second hand petrol 2.0)
( it is this replacement engine that carries the problem)

Would like to know a cause. Kind regards
Stephenn