Engine Rattles at Idle
 

I have a 2007 bmw 523i e60 with an N52 engine. The engine rattles at idle but there is no “Check Engine” light coming on the dashboard right away, it inly comes on after some time. When it comes on, it tells me that there is a misfire in cylinder 6. I tried to change the place of the ignition coil and spark plug of cylinder six and used them on cylinder 2, but still the check engine comes on and the code indicates a misfire in engine six, even after replacing. What can be the issue?

Injector, fuel pump, compression or vacuum leak

Are you using any software like INPA to diagnose? what is the fault code you are getting? There could be various reason as SeanJordan20 indicated.

You likely have a bad DISA valve. Mine was rattling, sounded like lifter ticks. Turns out it was a worn out DISA valve.

You can try the following to see if it fixes it. Top off your oil and add Liquid Moly Hydraulic Lifter Additive (can be found on Amazon). Idle your car for a minute and bring the car to about 3k RPM and hold it there for a minute or two. Check it after, you might get lucky and it goes away Sometimes you have to take it for a ride after. Mine was fixed by changing out the DISA valve, relatively easy procedure. But don't spend that money yet, try my fix.

My friend had a 330i 2005 and the tick went away after adding the Liquid Moly and letting it idle for a few minutes at 3k RPM, after he took it for a ride and it went away. If it does not fix it, it could be lifters, DISA valve, etc.

INPA won't give you a code with this, unless it is a more serious issue. Like a bad timing chain, etc.

It will just be an audible tick and won't even hurt the performance. If INPA is throwing engine errors and you notice bad perfromance, it is a more serious issue that needs to be addressed. I had a bad DISA valve, yet INPA did not tell me it had an issue. I switched my stock intake for a 3-stage intake while I was at it, it gains you some easy horsepower. My car definitely pulls harder at mid-rpm and seems to ring out the engine quicker, especially when I turn on Sport mode.