misfire at idle - worth chasing (n54 engine)

[AllanC 4]

Hi there,

i have an irregular misfire at idle on my 2008 135i N54, pulled the plugs and put new ones in (bosch bmw branded ones) and when pulling the plugs noticed that the plug on cylinder number 2 was alot darker and had more carbon on it than any of the other ones. Goes great when driving and no misfires at that stage, it's only noticeable at idle and fairly irregular then anyway. 

Is it worth chasing this or is it really not a big deal? From what I've read it's likely to be a leaky injector. Any bad long term effects from not sorting this out? Car is new to me but has 90,000km or so on it already. Will put a new set of coils in and do a walnut blast soon as I can justify the spend as unsure when that stuff was last done but doubt that'll fix it. Do you have to replace the whole bank if it's the injector?

Any advice appreciated. 
Cheers,

Allan

[Dogballs 115]

there was a lot of issues with bad coils around that era... it will show up as an error in INPA or other diagnostic software if it is a coil... the ECU will not always give check light until it occurs a certain amount of times... 

air leaks in the PCV system are not uncommon too...

Good luck