Does anyone have any ideas? (Sorry for the long post).

2.2 Turbo Diesel (DI) Electronic fuel pump.(Nissan Almera Tino 2002)

Is it the same engine in the 2.2 Diesel Primera and is the diagnostics OBDII
compliant.

Engine starts perfectly cold or warm.

Original problems occurred when running with engine cool until normal
running temperature acheived with temp gauge at halfway point.

Had changed oil to the tesco high grade 15w-40 previous to problem first
occuring.

The fault: Engine cool,increase throttle then at 1500 - 2000 rpm engine miss
fires and a cloud of white smoke thrown out of exhaust.

Once the engine is warm smooth running although occassionally a little
lumpy.

Once cruising along no problems at all.

Changed air filter, fuel filter and tested ECM and sensors (no fault code
indicated). All seems to be in order.

No oil loss or coolant loss.

Changed oil to a 10w-30 and although engine warmed quickly and the cool
running problem (coolant warmed more quickly) occurred for less time from
cold start.

The engine performed terrible when warm. Immediately took the 10w-30 oil out
(too thin).

Replaced with a 10w-40. Performs much better now.

Over the last week the ambient air temperature on a morning is much cooler
down to about 2 celcius.

The car is running much smoother and will even run when engine cool without
a problem.

Obviously something to do with cool air being denser,more air to fuel and
fuel being burned more efficiently.

The white smoke when fault occurs is more than likely unburned diesel is it
not?

Just one last thing to mention is that even when running well there is some
sort of a lag at just after 1500 rpm when applying throttle, but even this
was less noticable today when ambient air was cold.

Thanks for any suggestions.