Rattles and loss of power

My freelander 1 Td4 2006, if I hit the acc hard around 60mph + the engine seems to take on a rattle sound and I get intermitant loss of power, the rattling noise stays afterwards. It can make me nervous like the car is about to break down, but Upto now it has carried on going till home.
Any ideas what this could be

I have just had a look and the rattle noise could be the plastic cap on the alternator that seems loose.

if the rattle noise is 'diesel knock' [ do a youtube search if needed ]
that, together with a loss of power .. suggests a faulty injector ..
or possibly an issue with the fuel rail sensor.
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i.e. if it is diesel knock .. it possibly means that the pre-injection injector cycle is missing.

from .. diesel knock / pinking
" A problem resulting from worn parts or sticky nozzles are a delay in the start of injection or incorrect pre-injection which in turn results in rough running, diesel knock or pinking. "

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