[Melbowski]

Solved! The injector for cylinder two was bad/leaking. New injector swapped in and she runs like a champ again! Thanks for all the help and suggestions!

TL/DR: Idle sucks, randomly misses (nothing constant), almost stalls, then surges, sometimes just dies. Acceleration is fine, cruise is fine, idle sucks. New coils, plugs, valve cover, and a walnut blast did nothing. How do I check injectors/lpfp/etc? Suggestions?

Hi all, long read, but please bear with me. My 2012 335i xDrive has developed a serious surging/stalling/misfire issue over the last week. It started as a mild annoying miss right after startup that immediately cleared up, then over the course of a couple days started missing/surging at idle, and now misses, surges, and stalls. She won't stay running at idle at all now.

Things I've noticed: This only seems to affects idle. If I rev it up over 1k most if not all the missing clears up. No noticable issues under boost or cruise, no engine malfunction or reduced power messages on iDrive. CELs are multiple cylinder misfire, and cylinder 2/4/6 misfires.

Things I've tried: I initially figured it to be a vacuum leak or old plugs (not sure if previous owner ever changed them). I unplugged the MAF to force it into speed density/alpha N, but it made no difference whatsoever. I then changed the plugs to a fresh set, which also made no difference whatsoever. Then I decided to pressurize the intake, but found no leaks (I think I'll see about getting a smoker soon). Finally I hooked up ISTA and it ran some tests and concluded I should replace the cylinder 4 injector. Not sure how that'll clear up the other misfires, but I've got a couple spare injectors so I'll see about swapping and coding a spare into cylinder 4.

Other info: Only mods are stepped FMIC, MHD stage 1+, XHP stage 3, and aluminum charge pipe. Car has been running flawlessly with this setup for over a year.

So that's the story so far, any suggestions what to try next? I know idle problems are the bane of the N55, but I can't believe how suddenly it came on. Any help would be appreciated.

[TunafishE93]

You running burps and stock cats? Maybe a clogged cat.. Just a guess but it will get slowly worst.

[JTMMO]

Mine has a identical issue rn. Took it to the shop last night, so hopefully they'll find the fix.

[eurocarfan100]

Originally Posted by Melbowski

Hi all, long read, but please bear with me. My 2012 335i xDrive has developed a serious surging/stalling/misfire issue over the last week. It started as a mild annoying miss right after startup that immediately cleared up, then over the course of a couple days started missing/surging at idle, and now misses, surges, and stalls. She won't stay running at idle at all now.

Things I've noticed: This only seems to affects idle. If I rev it up over 1k most if not all the missing clears up. No noticable issues under boost or cruise, no engine malfunction or reduced power messages on iDrive. CELs are multiple cylinder misfire, and cylinder 2/4/6 misfires.

Things I've tried: I initially figured it to be a vacuum leak or old plugs (not sure if previous owner ever changed them). I unplugged the MAF to force it into speed density/alpha N, but it made no difference whatsoever. I then changed the plugs to a fresh set, which also made no difference whatsoever. Then I decided to pressurize the intake, but found no leaks (I think I'll see about getting a smoker soon). Finally I hooked up ISTA and it ran some tests and concluded I should replace the cylinder 4 injector. Not sure how that'll clear up the other misfires, but I've got a couple spare injectors so I'll see about swapping and coding a spare into cylinder 4.

Other info: Only mods are stepped FMIC, MHD stage 1+, XHP stage 3, and aluminum charge pipe. Car has been running flawlessly with this setup for over a year.

So that's the story so far, any suggestions what to try next? I know idle problems are the bane of the N55, but I can't believe how suddenly it came on. Any help would be appreciated.

Change the coils and or spark plugs for those cylinders. Most likely coils! It’s really easy fix, you need to main remove the plastic engine cover, remove few clips and be able to change the coil. Easy diy on the forums.

[JTMMO]

Just fixed my issue it was the injector on cylinder 1

[Melbowski]

Originally Posted by TunafishE93

You running burps and stock cats? Maybe a clogged cat.. Just a guess but it will get slowly worst.

I am running the PPK burble, but that's cat safe I thought? So I checked the exhaust and I don't hear our see anything. There doesn't appear to be any loss of power either, just crap idle. There is a light sulfer smell, but that could be from it missing too. I'll probably pull the exhaust when I get it on a lift to check it out more thoroughly.

Originally Posted by eurocarfan100

Change the coils and or spark plugs for those cylinders. Most likely coils! It’s really easy fix, you need to main remove the plastic engine cover, remove few clips and be able to change the coil. Easy diy on the forums.

I think this is my next line of attack; I already did plugs as per my first post, but I skipped the coils so I'll order up a set. Keeping my fingers crossed that it's just this simple.

Originally Posted by JTMMO

Just fixed my issue it was the injector on cylinder 1

Thank you for the report, I'll keep an eye on my injectors. I ended up finding that the boot on coil 4 was all messed up and not seating properly. Probably my fault when I changed the plugs... Got that squared away and now my constant miss is gone, just the random miss with crappy idle remains. AFR doesn't fluctuant much other than when it misses so I'm not sure if an injector is going, but it's on the table. I'll see what ISTA can do to test the injectors.

I'll keep the post updated with what I find out. If coils don't do it, I'll be getting a smoke tester. Thanks for all the input

[Melbowski]

So new coils and plugs are in and it didn't change a thing (needed done anyway though). Car still surges, wants to stall, and misses at idle. The miss is random, not constant. Zero codes. Car accelerates fine, cruises completely fine, but idle is still terrible.

I am completely at a loss as to what the problem is. How do you determine if an injector is bad when it doesn't have a constant miss? Any way to definitively test them? I guess a smoke test is my next option, then I'll be completely lost.

Are there diagnostic DIYs for idle here? I mean I can test anything needed, I just need to know how to test it and what I'm looking for. Idle problems sure are a pain. Thanks for the help and suggestions so far.

[Melbowski]

Just keeping updates as I keep trying to fix this idle issue. So I put a new valve cover on (needed it anyway) hoping it was a valve cover leak or bad pcv. No such luck, random idle miss refuses to go away. Not sure where to go from here.

I found a post with some vague directions on cylinder tests with INPA, so I guess that'll be next on the list. So annoying that it just popped up suddenly with no codes or anything to point me in the right direction. Only upside is I was planning to replace my coils, plugs, and valve cover anyway so at least that's done now XD

I'll keep updating to hopefully help someone else in the future with a similar issue. If anyone has some concrete directions on how to test each cylinder with INPA and more importantly what numbers I'm supposed to be looking for, I'd really appreciate it.

[Dovydas.B]

I am interested if you can test the injectors on N55 using INPA/ISTA

[TunafishE93]

I looked on ISTA but didn't see a test for the N55, maybe INPA.. I test mine with Protools that I can log, so no need to look further.

[Melbowski]

Another update, I decided to walnut blast the intake valves, and man were they nasty! On the upside they're nice and clean now, but on the downside it didn't do jack for my idle issues... Still zero codes, so no help there.

As mentioned before, my exhaust smells rich and I see that my fuel trims are pulling fuel, so perhaps it really is an injector. I read that they use a special one-time-use seal, so I abandoned the idea of just trying to swap them out willy-nilly. That begs the question though, how the hell do I figure out which one is bad? Can anyone point me to a guide on how to diagnose which injector is bad? I'd be happy to change it if I knew which one it was.

[bobbby]

I have a 2011 e90 n55 mhd stage 1+ and had a rough idle with car dying randomly. Sent it to my mechanic and he found that my vrsf chargepipe had blown through a bolt on the bottom, which plugs a hole I believe is designed for another add-on.

They put a washer and bolt on that to close the opening and haven't had the idle issue since. Not sure if this is your issue but perhaps take a look at your chargepipe

[carguy138]

Originally Posted by Melbowski

TL/DR: Idle sucks, randomly misses (nothing constant), almost stalls, then surges, sometimes just dies. Acceleration is fine, cruise is fine, idle sucks. New coils, plugs, valve cover, and a walnut blast did nothing. How do I check injectors/lpfp/etc? Suggestions?

Hi all, long read, but please bear with me. My 2012 335i xDrive has developed a serious surging/stalling/misfire issue over the last week. It started as a mild annoying miss right after startup that immediately cleared up, then over the course of a couple days started missing/surging at idle, and now misses, surges, and stalls. She won't stay running at idle at all now.

Things I've noticed: This only seems to affects idle. If I rev it up over 1k most if not all the missing clears up. No noticable issues under boost or cruise, no engine malfunction or reduced power messages on iDrive. CELs are multiple cylinder misfire, and cylinder 2/4/6 misfires.

Things I've tried: I initially figured it to be a vacuum leak or old plugs (not sure if previous owner ever changed them). I unplugged the MAF to force it into speed density/alpha N, but it made no difference whatsoever. I then changed the plugs to a fresh set, which also made no difference whatsoever. Then I decided to pressurize the intake, but found no leaks (I think I'll see about getting a smoker soon). Finally I hooked up ISTA and it ran some tests and concluded I should replace the cylinder 4 injector. Not sure how that'll clear up the other misfires, but I've got a couple spare injectors so I'll see about swapping and coding a spare into cylinder 4.

Other info: Only mods are stepped FMIC, MHD stage 1+, XHP stage 3, and aluminum charge pipe. Car has been running flawlessly with this setup for over a year.

So that's the story so far, any suggestions what to try next? I know idle problems are the bane of the N55, but I can't believe how suddenly it came on. Any help would be appreciated.

I had a very similar issue. Check the plug on the TMAP (on the charge pipe). Corrosion/oxidation on the pins will do exactly what you are describing. Some dieletric grease on the pins is a good idea too.

Unfortunately the location of it makes it easy for water to get in.

[Melbowski]

JTMMO freaking called it! I got looking into the fuel trims and noticed it was pulling fuel hard, so I commenced to pulling the spark plugs and cylinder two was soaking wet with gas. Swapped in a spare injector, coded it, and after a couple minutes it evened the fuel trims out and idles smooth again! Took it for a gentle spin so it could even out the cruise fuel trims, and she seems better than ever! (probably from all the new parts and maintenance XD)

I let the car sit for a couple weeks before doing the spark plugs the first time, so cylinder 2 wasn't wet or smelly when I originally pulled it. I won't make that mistake next time.

Thank you all so much for your help and suggestions! I also checked my charge pipe and tmap as suggested; the meth injection plugs are both tight and leak-free and the tmap looks clean but I put some dielectric in it just in case. Thanks again, hopefully this can help someone else in the future.

[autoart]

You might want to check your oil for a gas smell and/or change it.