High rpm misfire cyl6 - all new parts

[Zazanzabar]

Normally I wouldn't be one to ask for help on my car as I like to figure things out myself but I am at my wits end on this one.

I have an 07 335i mt that is sitting at 102k km and is full bolt ons, so inlets, outlets, 5.5 inch intercooler. I am running a jb4 + mhd bef on stage 2 and have a consistent misfire (only cylinder 6 every time) just above 6k rpm in any gear above 2nd. Since my taking of ownership two years ago I have preemptively changed out almost every part to get ready for a single turbo sometime next year. Brand new index 12s, a new hpfp, a walbro 450 lpfp, new fuel pressure regulator, Eldor coils, ngk one step colder plugs and some more items that are likely not pertinent to the issue at hand.

With all these new components I still have problems with the hpfp taking a dump past 6k rpm. The low pressure side is fine as far as I can tell but the high pressure side abruptly drops after 6k rpm to under 1500psi or in the case of the log 1350psi. The car goes into limp mode and either displays a misfire code for cylinder 6 or it comes up with no codes at all which doesn't make it easy to pinpoint a smoking gun.

Living in Canada, I don't have access to e85 so I'm running shell 93. I figured that the hpfp would have no issues at all keeping up on pump with stock turbos but maybe I'm wrong.

Does anybody have any idea why my hpfp seemingly can't keep up?

datazap.me | Zoridox | N54 6200rpm Misfire HPFP Crash

datazap.me

 

[carabuser]

Was the injector port OK on cyl 6 when you replaced the injectors? Ovaling is a possible cause of misfires.

The log isn't much use because JB4 doesn't show any of the important channels when it comes to diagnosing issues like this, and it only records at 2Hz. You really need to see the torque limit and fuel mode parameters. The fuel pressures also don't make sense, I don't know why they the JB4 just shows a random integer instead of just showing the actual pressure in the rail.

Since you are stock turbo I suggest just removing the JB4 and running an OTS map. Then we can see what the car is actually doing.

 

[Zazanzabar]

When I changed out the old index 1s there was no evident blowby and the bore seemed perfectly fine. I don't think they had ever been pulled previously so the bore should be fine.

The jb4 might have to get pulled until the single goes in. If I have time I'll do that today and see if I can get another log in with an MHD ots map for some better data. I honestly wouldn't be surprised if changing to an ots map just fixed the problem.

 

[Zazanzabar]

Was the injector port OK on cyl 6 when you replaced the injectors? Ovaling is a possible cause of misfires.

The log isn't much use because JB4 doesn't show any of the important channels when it comes to diagnosing issues like this, and it only records at 2Hz. You really need to see the torque limit and fuel mode parameters. The fuel pressures also don't make sense, I don't know why they the JB4 just shows a random integer instead of just showing the actual pressure in the rail.

Since you are stock turbo I suggest just removing the JB4 and running an OTS map. Then we can see what the car is actually doing.

Here's an updated log using a v10 stage 2+ 93oct ots map. rail pressure still crashing at 6200rpm so I'm at a loss unless the hpfp is faulty even though it's new. Any ideas would be amazing, I'm really hoping to get it running right for a track session in the coming months.

datazap.me | Zoridox | MHD 6k rpm misfire

datazap.me

 

[carabuser]

Your rail pressure is fine. The pressure drop at the end of the run is a result of the misfire, not the other way around.
If you add the fuel mode parameters in then you'll probably see the fuel mode jump to mode 15 which is limp.

The log doesn't show any issues, in fact it looks really healthy. You've replaced all ignition related components so it's nothing obvious. Sometimes people get cylinder 6 misfires when their flywheel goes bad, that's all I can suggest.

 

[Zazanzabar]

Your rail pressure is fine. The pressure drop at the end of the run is a result of the misfire, not the other way around.
If you add the fuel mode parameters in then you'll probably see the fuel mode jump to mode 15 which is limp.

The log doesn't show any issues, in fact it looks really healthy. You've replaced all ignition related components so it's nothing obvious. Sometimes people get cylinder 6 misfires when their flywheel goes bad, that's all I can suggest.

Thanks for the input, it's nice to hear the motor is running well outside of this issue. I figured at 102k, stock turbos and pump gas that the flywheel wouldn't be the issue but with the stage 2+ tune in 4th I was getting some clutch slip so I might be due for a clutch job anyways.

I'll double check the spark plug gap and maybe bring it down a smidge to see if that changes anything otherwise I suppose I'll just have to short shift until I do a clutch and flywheel.

I did want to ask, if it was a mosfet issue since I have an msd80, I assume there would be accompanying codes for it right?

 

[Sgop335]

bank 2 negative stft separation seems suspicious, injectors coded correctly? any leaky ones?

 

[Zazanzabar]

bank 2 negative stft separation seems suspicious, injectors coded correctly? any leaky ones?

Yes I made sure to code the injectors when I replaced them. I haven't checked if any of them are leaking and I have some misses on a cold start so I might check them when I get the chance. I assumed there'd be some afr shenanigans if they were leaking but I also would think they'll all be fine as they're all brand new index 12s from fcp.

I did notice the variance too and am wondering if it could be something as simple as an upstream o2 on its way out.

 

[Tzaks]

You could try a full reset of lambda adaptations using INPA, it's not the same as using MHD to reset them. I had a recurrent problem running rich with a couple of codes coming up and this cured it. Vehicular DIY has a good video on how to test the lambda sensors.

Good compression across all cylinders? Have you tried swapping coils/plugs around? I know you said you replaced them but maybe you got a bad coil/plug on #6.

 

[Jern54]

I had the same issue once.
Misfire at 6800RPM with a fairly new index 12 injector.

Dropped in a new one and the issue was solved.

 

[pbondar]

These seem pretty mysterious…I had this and subsequently discovered my Nexsys B58 coil bracket has vibrated loose and it was rattling across the back of the engine..no misfire since then..but..haven’t gone back to my really ‘spicy’ tune that provoked it the most..must get around to trying it..I do have the lighter M DCT DMFW to fit which is alleged to be the all time cure..