Rattle noise from diesel mazda 6 2008 when in idle no noise when it revs

first question --diesel or petrol
diesel can be injection too far advanced/ excessive fuel (crank position sensor or injector control module)
petrol ignition timing too far advanced
crank position sensor , air /fuel ratio causing detonation
in both cases run the fault codes first
the noise will be there when traveling but the vehicle noise covers it
have a compression test done to check for worn cylinders and rings producing piston slap

it sounds like the duel mass flywheel has gone bad unless there is something fouling ie .exhaust so get the exhaust etc first cos a new flywheel/clutch is a EXPENSIVE JOB! GOOD LUCK

check for wires to the idle/fuel control module on the pump

What kind of vehicle ? Which engine? Need more info.

I would check exhaust system for loose heat shields or bracket.

i would check all the basics like spark plugs and check for vacuum leaks around the intake manifold.With a can of 2+2 carb cleaner while engine is running --if idle goes up or down that is were your leak is--
check egr too, Lee

it could be a loose pipe on the turbo. the noise would get louder with higher revs as with higher revs higher boost is produced. check for loose pipes and give them a tighten then try a test drive. hope it helps you

explain rattling noise. you can take off the fan belts. start engine briefly to see if engine stil makes noise. that will tell you if its engine or the acc.

Check to see if the valve lifters are not making the noise. Turn on the engine and rev it up to about 1500 rpms and see if the clicking is coming from the valve cover area.

possibly the cat itself broken up and rattling in side the silencer especially if more noticeable when engine warmed up.