Mystery idle issue

[jimmyybob2]

My 740 has a bit of a cough. When it’s idling there is a momentary hiccup like a loss of ignition, it’s tiny and only a millisecond but it makes the engine jump for a split second, it happens every 5-10 seconds when stationary. Seems to drive fine no issues no smoke and smooth.???

[shogun]

here is a DIY how to test the coils on BMW engines https://www.youtube.com/watch?v=JLDo7Jk78ac
also remove the spark plugs and see if one looks different in colour