Nightmare diagnosing n54

Msport335

Specialist
Jun 7, 2018
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Need everyone's tuning expertise ! Brand new index12s , plugs , coils and 4 new o2's and still getting rough cold starts which feel like small misfires...like wtf

Now getting 2c3d and 2caa codes....everything is new just days old

Help is greatly appreciated
 

Msport335

Specialist
Jun 7, 2018
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Tell us about the car - year/model/miles - mods. Was it doing it before the updates? And for how long? etc ...

Filippo


2009 335i FBO/LSD/PS2/METH 85k miles / 136k kms on the car

prior to changing everything i suspected there were leaking injectors as afrs would not climb to 234.95 when i let off throttle and was also having light throttle stuttering around 3k rpm (which was most likely a number of small misfires like your driving over a very bumpy road)
so i proceeded to replace everything , index 12s, coils, plugs, 4 Bosch o2 sensors and BMW lpfp sensor. hpfp and lpfp are running perfectly fine at idle, cruising and wot pulls so no concern there.

car started having rough cold starts after all the new stuff was installed and threw coldstart misfire codes in cylinder 3&4.

i swapped coils to see if misfires followed....they did not.

i then proceeded to replace the brand new injectors in 3&4 with older index 12s in working order. next morning coldstart was fine ...no misfire in 3&4 however now misfires in cylinder 1&2.

so i swapped out the new plugs in 1&2 with a couple old plugs i had which were in good shape (all NGK 95770)

next mornings cold start was ok....no misfires but still stumbling a bit.

this mornings cold start was the same as well...drove to work...all ok by the looks of things. drive home from work and all of a sudden notice bank 1 AFR stuck around 20:1 and stft1 froze at 0. cleared codes while driving and they came back shortly after (did this again over and over till i got home)
 

Msport335

Specialist
Jun 7, 2018
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what points to a vacuum leak?

vacuum at idle is normal and boost builds just fine during pull
 
Last edited:

Msport335

Specialist
Jun 7, 2018
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here's a log with everything new installed ....just yesterday got 2c3d and 2caa codes

https://datazap.me/u/msport335/94-octane-pure-stg2-v2?log=0&data=3-22

just swapped out bank1 pre cat o2 due to the codes from yesterday and pulled a few logs... also put the brand new injectors back in cylinders 3&4. noticing the AFR's in a couple of these logs don't hold steady at 234.95 when i let off....they start to fall back down again..... keep in mind these are brand new index 12s from FCP euro which were installed last week.

any ideas?

https://datazap.me/u/msport335/pure-stg2-94-octane-v2?log=2&data=3-22
 

Maximum96

Private
Jul 21, 2017
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Check all pins in DME connectors, I remember some one had exact problems and pins were pushed in
 

Msport335

Specialist
Jun 7, 2018
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Check all pins in DME connectors, I remember some one had exact problems and pins were pushed in

I'e never even opened up the DME....how could the pins be affected. Do you mean the connectors off the wiring harness that plug into the DME?
 

Msport335

Specialist
Jun 7, 2018
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Stumbling cold start this morning but no codes. I have a suspicion that a couple of these brand new injectors are leaking but I don't know which and that' causing the rough cold starts and causing the afr's not to shoot right back up to 234.95 when I let off throttle....sometimes it does but sometimes not. Do I say F it and reorder 6 new ones from fcp and send these back to them?
 

doublespaces

General of the Army
Oct 18, 2016
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2009 E93 335i
you could try pulling the injectors and doing the starter test with injector harnesses disconnected
 

Maximum96

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Jul 21, 2017
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you could try pulling the injectors and doing the starter test with injector harnesses disconnected
It's a great test, but I urge to replace injector seals after that, and replace it with the proper procedure, I did not know that and caught it quick enough not to bore out my injector hole from a burned up seal!
 

Msport335

Specialist
Jun 7, 2018
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It's a great test, but I urge to replace injector seals after that, and replace it with the proper procedure, I did not know that and caught it quick enough not to bore out my injector hole from a burned up seal!
Is this test legit ? Cuz I just left my new injectors in the head and tested my older index 12s this way by unplugging injector harness and coils and cranked it over a number of times...... surprised that o didn't see one of them leaking ......fairly certain I got the procedure right. As i was cranking, there was plenty of pressure according to fuel rail pressure monitor via mhd. No leaks .... y did I purchase new injectors of my old index 12s look to still be good... maybe it was o2s all along?
 
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matreyia

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Apr 19, 2017
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Is this test legit ? Cuz I just left my new injectors in the head and tested my older index 12s this way by unplugging injector harness and coils and cranked it over a number of times...... surprised that o didn't see one of them leaking ......fairly certain I got the procedure right. As i was cranking, there was plenty of pressure according to fuel rail pressure monitor via mhd. No leaks .... y did I purchase new injectors of my old index 12s look to still be good... maybe it was o2s all along?

sometimes a super small detail that was missed will produce headaches.

1. when installing injectors - did you install each one in the bore hole within 30 seconds or less after taking off the cap?
2. after taking off the cap, did you also push the injector into the smallest o-ring containment hole on the injector tool in order to compress the seals even more than the published amount? If this was done, then the injector(s) should have seated into the engine fairly easily with very little effort.
3. was there any resistance that was beyond "normal" resistance when inserting the affected injector holes? if so, did you make sure that the injector was absolutely seated fully on those holes?
4. was there a lot of gunk in the area immediately surrounding the injector bore holes upon removal of the injectors? If so, some debris could have been caught between the borehole walls and the new injectors.
5. Was there any oil in the injector area where each came out?
6. the bendable braces were reinstalled with correct orientation? where the bolt forces the bended part against the injector base to keep them perpetually braced downwards?

if all were done, then could be a vacuum leak as previously stated.
 
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