N55 FBO PS2 odd engine 'stumble'

jlegelis · 01-08-2020, 04:09 PM

Gents - Car is an FBO E92 N55 XDrive 6MT w/ PS2, Stage 3 tune, 66k miles - recent build so still trying to debug. Under full throttle car feels like it occasionally stumbles or misses for a split second - feel it mostly through the seat. No codes, no lights, no misfires, and data logs look clean - car otherwise runs perfectly so not really sure where to begin.

Thoughts: Coils are original, plugs are 15k old and gapped to .022. Any usual suspects - really hate to start randomly guessing, but don't have a lot else to go on? Wisdom or good suggestions appreciated.

-JohnL
Boston

E92n55slo · 01-08-2020, 04:19 PM

Your coils are at 66k? Replace those antiques. Also what do you mean by stage 3 tune?

jlegelis · 01-08-2020, 05:00 PM

>> Your coils are at 66k? Replace those antiques.
Stock or aftermarket? What else while I'm in there?

>>Also what do you mean by stage 3 tune?
Custom tune by Wedge. I call it that because it's a bit more aggressive than the MHD Stage 2+ OTS maps.

9krpmrx8 · 01-08-2020, 05:06 PM

Your FBO PS2 on original coils and 15k plugs? I'd start there, you never tune on worn ignition components. And I hope you are running a proper custom tune, no clue what "stage 3" is.

E92n55slo · 01-08-2020, 07:09 PM

Quote:

Originally Posted by jlegelis

>> Your coils are at 66k? Replace those antiques.
Stock or aftermarket? What else while I'm in there?

>>Also what do you mean by stage 3 tune?
Custom tune by Wedge. I call it that because it's a bit more aggressive than the MHD Stage 2+ OTS maps.

Your ps2 so you can run stock coils no problem or upgrade to precision raceworks coil kit if you want.

C2YT · 01-09-2020, 07:29 AM

Change your plugs to NGK-97506, they are a step colder I believe. It is what was recommended to me when I installed my PS2.

I believe the gap is .022 as well. I would connect with Wedge and have them review a log. It should be easy to see if it is a misfire due to ignition...

Every car is different, but I don't push pas 18 psi on pump 93. E30 I bump to 20-21 PSI. It is possible you are getting spark blowout depending on how much boost you are making. Or you could be crashing your HPFP causing it to stumble and misfire.

When you build a car like this you need to be aware of how it functions and know how to read a log. This way you are able to make your own diagnosis and don't take the chance of hurting the engine.

Turbod · 01-09-2020, 04:04 PM

Stumbles are usually ignition or fuel. I would start with replacing the coils. C2YT is right about the gap. Ideally you want to run the largest gap possible without running into blowout.

01-08-2020, 04:09 PM	#1
jlegelis Private First Class 33 Rep 129 Posts Drives: 2013 E92 N55 MT MSport Join Date: Jan 2013 Location: Boston, MA iTrader: (0)	N55 FBO PS2 odd engine 'stumble' Gents - Car is an FBO E92 N55 XDrive 6MT w/ PS2, Stage 3 tune, 66k miles - recent build so still trying to debug. Under full throttle car feels like it occasionally stumbles or misses for a split second - feel it mostly through the seat. No codes, no lights, no misfires, and data logs look clean - car otherwise runs perfectly so not really sure where to begin. Thoughts: Coils are original, plugs are 15k old and gapped to .022. Any usual suspects - really hate to start randomly guessing, but don't have a lot else to go on? Wisdom or good suggestions appreciated. -JohnL Boston
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01-08-2020, 04:19 PM	#2
E92n55slo First Lieutenant 45 Rep 283 Posts Drives: 2011 e92 335 x drive 2016 m2(s Join Date: Sep 2017 Location: NJ iTrader: (4)	Your coils are at 66k? Replace those antiques. Also what do you mean by stage 3 tune?
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01-08-2020, 05:00 PM	#3
jlegelis Private First Class 33 Rep 129 Posts Drives: 2013 E92 N55 MT MSport Join Date: Jan 2013 Location: Boston, MA iTrader: (0)	>> Your coils are at 66k? Replace those antiques. Stock or aftermarket? What else while I'm in there? >>Also what do you mean by stage 3 tune? Custom tune by Wedge. I call it that because it's a bit more aggressive than the MHD Stage 2+ OTS maps.
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01-08-2020, 05:06 PM	#4
9krpmrx8 Clean is the new cool, keep it that way. 808 Rep 1,685 Posts Drives: 11' Alpine White 335i Sedan Join Date: Jan 2016 Location: San Antonio, Texas iTrader: (0)	Your FBO PS2 on original coils and 15k plugs? I'd start there, you never tune on worn ignition components. And I hope you are running a proper custom tune, no clue what "stage 3" is. __________________ 2011 335i, FBO, N55+ Turbo, full E85, S55 intercooler, etc. 2015 X5 35i Xdrive
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01-09-2020, 07:29 AM	#6
C2YT Private First Class 68 Rep 159 Posts Drives: 2011 e90 335i Join Date: Dec 2017 Location: Taylor, MI iTrader: (0)	Change your plugs to NGK-97506, they are a step colder I believe. It is what was recommended to me when I installed my PS2. I believe the gap is .022 as well. I would connect with Wedge and have them review a log. It should be easy to see if it is a misfire due to ignition... Every car is different, but I don't push pas 18 psi on pump 93. E30 I bump to 20-21 PSI. It is possible you are getting spark blowout depending on how much boost you are making. Or you could be crashing your HPFP causing it to stumble and misfire. When you build a car like this you need to be aware of how it functions and know how to read a log. This way you are able to make your own diagnosis and don't take the chance of hurting the engine. __________________ 2011 BMW 335i E90 - FBO w/ Pure Stage 2 Turbo on JB4 BEF
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01-09-2020, 04:04 PM	#7
Turbod Major 396 Rep 1,210 Posts Drives: 2014 E84 X1 35i M Sport Join Date: Mar 2015 Location: Oregon iTrader: (0)	Stumbles are usually ignition or fuel. I would start with replacing the coils. C2YT is right about the gap. Ideally you want to run the largest gap possible without running into blowout. __________________ 2011 E92 335i \| 11.7@125 SOLD 2017 Camaro SS \| 12.7@114 SOLD 2019 Audi TT RS \| 10.5@130 SOLD 2020 F97 X3M \| 11.0@123 2023 G80 M3 xDrive
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