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      07-10-2020, 08:53 AM   #1
albatross_nlv
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Drives: BMW E88 N43
Join Date: Jun 2020
Location: Gelderland, Nederland

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Red face Help! Misfire cylinder 4, carbon deposit on spark plug cylinder 3

Hello everybody,

Iíve been browsing this awesome forums in the background whilst enjoying my 1series, but now I am in trouble myself so I guess itís time for me to step within this community. This is my first post within any forums ever.
Iíve been reading everything I can find on the forums, but couldnít get to a point where I am sure what the root cause is and the most recent discovery makes me doubt everything. I am technically gifted, but I am not working with engines every day. I believe I know what Iím doing but if I run into something that doesnít make sense then itís back to the planning board.

Iím driving BMW E88 118i N43

Lets get on to the problem:
Driving whilst on low revs (I remember driving for a while and only on/close to idle I got it. I got a misfire on cyl4 P0304. Another code said the burning duration was too short: P1304. Together with that came NOx sensor codes P124D, P122C, P121F P122F, P127A. Lambda codes P114B, P2196.
My first suspicion was carbon buildup on the intake valves. I had already replaced the coils on 3 & 4 (third was still using old Delphi coil that was completely rusted and the fourth cylinder had a misfire back then when I thought I fixed it.)

After looking at this I am quite confident it cannot be the carbon buildup. I am going to clean the valves during the weekend anyway, but now Iím looking past that.
However I decided to inspect inside of the cylinder to see if I can find a pattern and upon removing all of the spark plugs I noticed thereís a lot of carbon on the spark plug from cylinder 3.

Hereís the video of cylinders, I spot chipping on 3rd and 4th cylinder but I have very basic expertise so Iím not really sure what I should see or not.


I have ordered one refurbished piezzo injector and plan to replace the fourth injector, but as I see the carbon on the spark plug of cylinder 3 Iím not sure if I shouldnít replace the 3rd one as well.

I hope that I have provided enough info and that whoever takes the time to read it will have a great day. Iím personally running into a knowledge wall where Iím seeking someone who knows what Iím trying to describe.

If I had to guess I'd say injector 4 has a bad spray pattern/doesn't spray enough and injector 3 is leaking, but I don't know how to test this nor have any experience with this.

Also could someone advise me with a good book on direct injection?
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