N54 mystery misfire

Alexg5505 · 03-14-2018, 01:34 PM

Alright guys I know there’s a lot of threads on this topic, but I couldn’t find one pertaining to my exact issue. So I have a 2007 335i sedan (08/06) build date. I was running mhd stage 1+ with dcis for a while with no issues and decided I’d run the stage 1+ E30 map. Started having cylinder 6 misfires under heavy load so I replaced all plugs and coils. Problem persists and I switched back to the 93 map once the tank was empty. Still having misfires on 6

under heavier load, but sometimes it’ll happen at random times. Injectors were replaced by bmw under warranty a few years back and I confirmed they are not leaking... so I loosened the injector hold down for 5 and 6 and injector 6 seems to wiggle slightly with pressure compared to the others which do not wiggle at all. At this point I’m thinking my next course of action is new o-rings and decouplers. Any other ideas or things to check are appreciated. Thanks guys!

Pladi · 03-14-2018, 01:57 PM

It could be the injector, however if you are going as far as replacing the teflon seal and decoupler which i think the chance of just those failing is close to zero.. then might as well replace the injector.

But before replacing anything check compression on that cylinder.

BSM n54iS · 03-14-2018, 04:43 PM

LPFP - low pressure fuel pump. That E30 might've done it, maybe try re-flashing again or resetting the throttle mapping or some shit like that.

Alexg5505 · 03-14-2018, 06:07 PM

The lpfp is staying at a healthy pressure along with hpfp(which is newer). I have tried reflashing and am currently on the stage 1 tune which reduced the issue a little compared to stage 1+. The thing that gets me is that most people with injector issues experience stumbling and misfires on a cold start even at idle. Mine usually only does it under more load. Like 4th or 5th gear at 3kish warm or cold. I guess I’ll do a compression test and see how that turns out. What parameters are best to data log when diagnosing this?

Natemac19 · 04-21-2019, 11:02 AM

Quote:

Originally Posted by Alexg5505

The lpfp is staying at a healthy pressure along with hpfp(which is newer). I have tried reflashing and am currently on the stage 1 tune which reduced the issue a little compared to stage 1+. The thing that gets me is that most people with injector issues experience stumbling and misfires on a cold start even at idle. Mine usually only does it under more load. Like 4th or 5th gear at 3kish warm or cold. I guess I’ll do a compression test and see how that turns out. What parameters are best to data log when diagnosing this?

What seemed to be the issue? Exact same problem here.

03-14-2018, 01:34 PM	#1
Alexg5505 Registered 0 Rep 3 Posts Drives: 2007 335i Join Date: Feb 2018 Location: Naperville, il iTrader: (0)	N54 mystery misfire Alright guys I know there’s a lot of threads on this topic, but I couldn’t find one pertaining to my exact issue. So I have a 2007 335i sedan (08/06) build date. I was running mhd stage 1+ with dcis for a while with no issues and decided I’d run the stage 1+ E30 map. Started having cylinder 6 misfires under heavy load so I replaced all plugs and coils. Problem persists and I switched back to the 93 map once the tank was empty. Still having misfires on 6 under heavier load, but sometimes it’ll happen at random times. Injectors were replaced by bmw under warranty a few years back and I confirmed they are not leaking... so I loosened the injector hold down for 5 and 6 and injector 6 seems to wiggle slightly with pressure compared to the others which do not wiggle at all. At this point I’m thinking my next course of action is new o-rings and decouplers. Any other ideas or things to check are appreciated. Thanks guys!
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03-14-2018, 01:57 PM	#2
Pladi Lieutenant Colonel 718 Rep 1,753 Posts Drives: 2011 335i xdrive Join Date: Nov 2017 Location: Waterloo, ON Canada iTrader: (0)	It could be the injector, however if you are going as far as replacing the teflon seal and decoupler which i think the chance of just those failing is close to zero.. then might as well replace the injector. But before replacing anything check compression on that cylinder.
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03-14-2018, 04:43 PM	#3
BSM n54iS Brigadier General 2685 Rep 4,202 Posts Drives: '11 335is \| '16 Macan Turbo Join Date: Aug 2015 Location: Everywhere and Nowhere iTrader: (7)	LPFP - low pressure fuel pump. That E30 might've done it, maybe try re-flashing again or resetting the throttle mapping or some shit like that. __________________ '11 335is BSM MT "BMW Performance Editon" \| '16 Porsche Macan Turbo GruppeM CF Intake \| AR Resonated DP \| ER CP \| Turbosmart RacePort BOV \| Cobb FMIC \| RB Inlets \| RB External Mishi/Turner OCC \| Michelin PS4 \| BMW Performance Springs/Bilstein B8 + Dinan & M3 bits \| BMW Brembo BBK \| BMW Performance CF Spoiler \| BMW Performance CF Lip \| BMW Performance Alcantara \| PS Designs GTS Armrest \| AG H6-40 \| Rear Seat Delete
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03-14-2018, 06:07 PM	#4
Alexg5505 Registered 0 Rep 3 Posts Drives: 2007 335i Join Date: Feb 2018 Location: Naperville, il iTrader: (0)	The lpfp is staying at a healthy pressure along with hpfp(which is newer). I have tried reflashing and am currently on the stage 1 tune which reduced the issue a little compared to stage 1+. The thing that gets me is that most people with injector issues experience stumbling and misfires on a cold start even at idle. Mine usually only does it under more load. Like 4th or 5th gear at 3kish warm or cold. I guess I’ll do a compression test and see how that turns out. What parameters are best to data log when diagnosing this?
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