Multiple Engine Misfires Z4 35is

DaveN54Z4

New Member
Jun 26, 2023
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Can anyone help me understand what in the two logs below could be causing four cylinder engine misfires?


Plugs less than one year old, 4 coils from 2015 and other 2 (1 year new). Initially had 3 misfires, swapped coil from 5 to 4, now 4 joined the party. Some time ago also had a misfire on cylinder 2. Will swap all plugs and coils, but thinking it’s something else. AFR 1-2 stable/equal on idle, big gap when logging a pull. Plugs look clean, minor fuel smell when pulled out but not wet.

Car has 40.000 miles, rev 8 injectors, engine misfire>cel>rough/stutter until restart happened 1/3 times when stock, happens always now with stage 1 mhd ron95. Third gear acceleration, above 3000rpm, strong hesitation and engine stutter.

If 5 years ago, would have replaced injectors and hpfp anyways as preventive maintenance. Current prices make that a hard buy unless necessary.

Really would appreciate any feedback or suggestion as per the logs, 🙏
 

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carabuser

Lieutenant
Oct 2, 2019
849
1
745
0
UK
Ride
Z4 35i & 335i
Pretty textbook case of leaking injectors there. Replace them all before your oil gets diluted or you get left stranded when they stick open.
 

DaveN54Z4

New Member
Jun 26, 2023
3
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Pretty textbook case of leaking injectors there. Replace them all before your oil gets diluted or you get left stranded when they stick open.
Thank you for your reply

Could you please expand on what part of the graph makes it so obvious?

Left the car overnight after driving yesterday and on inspection this morning the plugs where neither wet and completely clean. No injector codes either.
 

carabuser

Lieutenant
Oct 2, 2019
849
1
745
0
UK
Ride
Z4 35i & 335i
The variance between banks under closed loop control and the spikes in bank2 afr.

Also when injection is shutoff in overrun the lambda reading is still showing fuel present in bank2.

Very clear cut IMO. Either change all 6 injectors and change your oil ASAP or sell the car. If you keep driving it like that you'll end up needing a new engine.
 
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DaveN54Z4

New Member
Jun 26, 2023
3
0
0
The variance between banks under closed loop control and the spikes in bank2 afr.

Also when injection is shutoff in overrun the lambda reading is still showing fuel present in bank2.

Very clear cut IMO. Either change all 6 injectors and change your oil ASAP or sell the car. If you keep driving it like that you'll end up needing a new engine.
Okay, that somewhat correlates with excessive burbles despite lowering them to zero.

Any observations or comments over HPFP? Seen as a failing unit also causes heavy stuttering above 3000rpm