Hi i'm new to this but could really do with some help!!

I've got 1998 2.0 diesel freelander which started to briefly lose power at about 3000rpm and now won't rev cleanly at all.

Could anybody help me narrow the problem down maybve this is a common fault?

Check or change yer fuel filter

Does the red engine management light come on at the same time?
Is it puffing big clouds of smoke?
It could be a fugked turbo or your crank position sensor,from my experience.
Have you had work done to your fuel pump/ timing belt?

Dont know if a stuck throttle position sensor would cause this problem.
A leaking injector,an open/dirty connector on the wiring loom.Could be a good time to clean all the earths in the engine bay.

Lots of things it might be,people here might rule out some of the things I've mentioned.It would have been better if this was posted in the freelander section.

Welcome to landyzone.If you dont have one invest in a haynes manual.

another option is that it could be the mass air flow sensor, I had this problem on my 2001 Td4 freelander. lack of power etc. I imagine this could well be the problem if you can rule out the other suggestions mentioned above