N54 misfire

[Mandinca]

I apologize in advance if this has been covered, I looked around and didn't see a thread which exactly matched my problem, only one that was resolved by doing what I have already tried.

So, when hitting boost at WOT or even close to it, I get a misfire...pick a cylinder, one through six....
First time it happened it was #3 so I moved the coil pack to #1 and tried again - the misfire followed the coil pack so I bought a new OEM Bosch from NAPA and put it in. Next time I went WOT it happened again on a different cylinder.....rinse, repeat, rinse repeat....now I've changed them all and it's still doing it.
Also, if I pull over and use MHD to reset codes the problem goes away until I boot it again. Another thing, if I don't pull over to reset it and just drive slowly it will reset itself after a minute or two. Is the ECU sensing a problem and cutting power to the coil for a couple of minutes until something in the ECU cycles and it resets ? I have no idea, just spit-balling.

I must point out that I am using OEM injectors which are a mix of 7 and 8 but I don't think that would cause this since the code moves with the coil pack which is currently causing the code.

One other thing, coding....a couple of my injectors are refurbished and I doubt they were coded when installed....and, even if they were, as they are refurbished what's to say that the codes printed on the injector body are actually correct anymore ?

TIA

[thibb001]

Maybe the coil pack you bought is faulty. Have you replaced spark plugs also? As for the injectors i would try to code them asap, it's not hard to do if you have a windows computer.

Hope this help, goodluck

[JM98]

Missfire issues are typically the easiest to avoid on this platform, but I regularly see people struggling with them. My advice to anyone buying an N54 is to immediately replace coils and plugs and start logging periodically. If you see variance in trims from bank to bank then replace all 6 injectors and code. Those three things will eliminate 99% of issues and make the N54 ownership experience much easier and enjoyable.

[Mandinca]

I replaced the plugs maybe 15,000 miles ago and the problem has been happening before and after I changed them. Also, all six cylinders have now experienced this issue so all six coil packs have been changed, one by one.
If it was one or two of the plugs then it would be the same cylinder each time. Also, when this first happened I moved the plug from the faulty cylinder and the misfire didn't move. I then swapped coils and it moved with the coil....so, coil failed, not the plug or the harness connection to the coil itself...right ?

I know there are some how to's on coding on the forum but for one thing it seems largely hit and miss (and requires a bit of tech geekery to make it work) and for another thing at least one of my injectors is a refurb so who knows if the codes on the injector housing are even accurate.

[JM98]

Originally Posted by Mandinca

I replaced the plugs maybe 15,000 miles ago and the problem has been happening before and after I changed them. Also, all six cylinders have now experienced this issue so all six coil packs have been changed, one by one.
If it was one or two of the plugs then it would be the same cylinder each time. Also, when this first happened I moved the plug from the faulty cylinder and the misfire didn't move. I then swapped coils and it moved with the coil....so, coil failed, not the plug or the harness connection to the coil itself...right ?

I know there are some how to's on coding on the forum but for one thing it seems largely hit and miss (and requires a bit of tech geekery to make it work) and for another thing at least one of my injectors is a refurb so who knows if the codes on the injector housing are even accurate.

Have you logged AFR's? They will show if you have a bad injector.

[Mandinca]

Originally Posted by JM98

Have you logged AFR's? They will show if you have a bad injector.

If I pull a log will you be able to read it for me, I've no clue when it comes to logs. However, that said, I'm not sure I can pull a WOT log if it goes straight to the misfire when I mash it.
I suppose I can replace the coil pack on the latest cylinder to have an issue and pull a log immediately.

As for injectors, I can't see that's the issue if the error moves with the coil pack if I just switch the coils around and try again.

[BMWL0VE]

How long has it been since the last time the vehicle ever had its intake valves cleaned? My valves were soo gunked with oil and carbon their was barely room for air to get into the cylinder head. that can cause it, also if you have a new coils and spark next step is check injectors. I would go with the cheaper route first (intake valve cleaning) and see if that fixes it then move to injectors.

[dsocold]

thats why you should just buy a coil and plug kit from fcp euro and change them all again anyway and this way you are covered for free replacements for life so you can swap again for next to nothing. I have an n54 pwrd car for 9 years now and I have never had a misfire issue, only when i first tuned it at 35k miles on my odometer and dealer replaced all 6 plugs coils and injectors and since then all i have done is coils and plugs 2 times and not because of misfires but as a preventative measure.. I got 155k on the odometer now..