Engine tapping from cold start

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Hi all,

I've just bought a 2006 Pathfinder Diesel Sport Auto.

From a cold start there is a prominent tapping from the engine bay for the first 5 mins of driving.

Once it's warmed up the noise goes away.

My first Pathfinder, so looking for some guidance/tips.

*edit* just to add the tapping increases with throttle

Many thanks

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after closer observation, the tapping is only when accelerating.

no tapping at all when idle, or holding revs, but then goes once the engine has warmed.

any advice would be greatly appreciated