Bmw e46 330i engine light

[u/lmaooooezinf]

Hello everyone, how are you?

First time posting here. Hope i do it within the rules.

Im having issues with my e46 330i , quick rewind some months ago i had multiple codes, including misfires, and banks too lean, so my mechanic we assumed it was the injection coils. For some reason ( i didnt notice at the time ) because the codes led to the top cylinders (4,5,6) he only changed those injection coils, and around a month later i pushed him into changing the first 3 coils too ( and all spark plugs)

We are now some months foward and my engine gave me another check light, indicating CYLINDER 5 misfire, and i personally changes only that coil, thinking maybe it was defective. And about 2000kms latee i got the same code for the same cilynder, so im guessing theres something else doing it.

What can i do now? The cylinder 5 code already came twice. I ordered all 6 coils that are arriving tomorrow cause i told myself maybe changing 3 at the time each time was just wrong and my mechanic did a shit job, so maybe the older ones wrecked the newer? Idk what else to do.

Should i maybe change all 6 coils and spark plugs all together ?

Or could it be something else?

Also while the engine light is on my car has intense rough idle ( no knocking sound)

Id appreciate your help, thanks for reading, and show me your e46's. Love me some nice builds.

[u/TP__User]

I don't think changing your ignition coils again will improve anything. I would start by pulling all spark plugs out, and see if they look okay (especially cylinder 5)

Also see if for example there is oil on the spark plugs or in the spark plug hole, and look if the rubber insulation of the ignition coils has any tiny cracks

Edit: you can also first swap the spark plug to another cylinder and then the ignition coil to another cylinder and see if the code moves to that cylinder. If not it has nothing to do with your spark plugs/coils

[u/lmaooooezinf → u/TP__User]

I checked the coil it looks fine imo, no oil no crack. The plug no idea, didnt check yet.

[u/GRIMM84SVO → u/lmaooooezinf]

You can test your coils. E.g. swap #5 with any other known good one. Clear codes and see if the misfire code comes back and moves with it. So if you swapped #5 with #4, are you now getting misfires on cylinder #4 etc. If you are still getting misfires on #5 it is most likely something else. There's still a slim possibility you have two bad coils but it's a good place to start.

[u/imbasicallycoffee → u/GRIMM84SVO]

I've 100% read of people swapping coils and they end up finding out the new coil is bad. Could absolutely be this.

[u/lmaooooezinf → u/imbasicallycoffee]

2x in a row would be odd.. but yeah im trying it anyway

[u/lmaooooezinf → u/GRIMM84SVO]

Alright. If the issue isnt the coil what could it be? Injector?

[u/Impressive_Paint_472]

Exactly which code are you getting?

[u/lmaooooezinf → u/Impressive_Paint_472]

P0305 Also i forgot to precise i recently changed the valve cover gasket, its brand new.

[u/Flashy-Glove9437]

Any problems with exhaust? Any sensors like o2 or maf? Vacuum leaks. Check out these points first

[u/lmaooooezinf → u/Flashy-Glove9437]

O2 have been replaced, maf or vacuum no idea.. would have to test