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      01-16-2023, 07:53 PM   #1
Dennyyv
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Mixture Codes And Misfires!

Hello, I am having a rather weird misfire issue with my 2007 335i, which I am hoping to get some input on.

Before i start explaining here's the Mod/maintenance list.

17t turbos (viv)
Inlets
Catch can
ARM Catless Dp (exhaust stock)
Pcv upgrade
bms dci cleaned 1000 miles ago.
ngk 2 step colder (12k miles ago)
Arm Charge pipe
5in ARM intercooler
injector Mosfets were repaired.
jb4 with mhd BEF
all vacuum lines were changed.


I've never really had any misfire problems like this before, other than maybe bad coil or bad spark plugs.
2 weeks ago I left the car sitting for 2 days, came back and started her up, ran fine no problem. 15 miles into my trip i get a flashing SES light on the dash and its misfiring bad.... I couldn't pull over any where because I was on a bridge with no shoulders, so i tugged it along looking for the nearest place to pull over while trying to think of what caused it, i had an mhd adapter in the car so while driving i scanned the car and codes came up as

29CD: Cyl 1 misfire
29CE: Cyl 2 misfire
29CF: Cyl 3 misfire
29CC: Misfire multiple cylinders (Hence the light flashing.)
29E0: Mixture Control
29E1: Mixture Control Bank 2
2C77: Oxygen Sensor after cat: signal
2C7B: Oxygen Sensor after cat: signal
Then some shadow codes for no catalytic converters. (Catless Downpipes but secondary cats are in place.) \

So about 2-3 min later i look up at the dash and the SES light is not flashing anymore but just on. and the car noticeably runs better about a minute after it went off completely.
Well not much else I can do so I decided to keep going, (stupid idea because i knew i had about 150 mi ahead of me to go but really had no choice...) it was fine for maybe 140 mi but the last 10 i got another SES light but no misfire but code for mixture control but only bank 1

29E0: DME: Mixture Control

I parked the car up because i was staying the night at the destination but the next morning i had to take the trip back home (150 mi: I was kinda scared Im not going to lie...)

the trip home was not filled with any misfires, but about an hour into driving i got the SES light once again. Same Bank 1 mixture code. cleared it and it was fine. I'm pretty sure its due to bad o2 sensors, and the car is definitely running rich as i can smell raw fuel from the exhaust pipe, but I never really payed attention to it because I thought it was because of de catted down pipes.
Anyways fast forward 3 days I'm driving it around all fine and dandy, until I start it up in the morning and I do know that I have a couple leaky injectors (index 1) but not to a point where its horrible at cold starts, it would maybe run a little rough (SOMETIMES) the initial cold start for about 5 seconds and then clear up and run completely fine- which was usual for about 2 years. cold start went as usual, let the needle drop and gave it another 5 min- start driving but 10 min into the trip very light throttle not giving it a lot of throttle, i notice it starts to misfire, 1 cyl and then the next cyl. run the codes and cyl 1-2 misfire.. limp it to work as i was running late and park up, leave it for 8 hours. come back to cold start it and boom misfiring cyl 1-2 like clock work, i live about 15 min away so I limp it home but when im just pulling up to my house the misfire and the SES light go away. i drive it around for another 5-10 min and no misfires. so I park it.

My first thought was- Spark plugs which i changed about 10-12k miles ago
I installed 2 step colder iridium ngk's when i first got tuned because it was misfiring after changing them and gapping them to 0.22 it went away ran good until now.
Pulled the plugs they were pretty black and beat up so definitely running rich but they looked okay, so i cleaned them up and put them in different cylinders to see if it would move. (honestly thinking about it now I didn't keep track of where i put them and it would be very funny if i put them in the same place... LOL) as well as the coils (but the coils I did in fact swap around for a fact.)
I felt as if i solved the problem by cleaning them because i drove it around for a day and i didnt have any problems. But no the problem did come back two days later.

My second thought was- Injectors. they are index 1's (not the worse but the oldest.) I found some dude selling 3 index 9's (yes i know this is the worst revision, but i only found that out after buying them...) for $120 and he told me 100x they were not leaking and they worked great and he pressurized the rail with them on and they had no drip or leakage. He only bought them to trouble shoot a problem but his problem ended up being ring lands causing a smokey exhaust, i trusted him and bought them I mean $120 for 3 injectors is worth a risk.
So i took out the Cyl 1 & 2 Injectors- they came out super easy all i had to do was pull on them with little to no strength.I did not put new seals just to trouble shoot it just for now, but it started running worse than it did before, and yes i did code the injector compensation values with ISTA, recoded all of the injectors. When i first started it, it was misfiring obviously but not enough to trip a SES, it was missing and running rough for longer and harder than my old index 1's did- every single time i would restart it not only on a cold start it would misfire for about 10-15 seconds as well as start surging and floating up and down with the rpm's. and then you can just feel it running rough and vibrating. Im not sure putting new seals on would do me any good at this point on those injectors, as when i pulled my old injectors out the seal was completely flat, and 10x worse than the index 9's and the tips were covered in soot. and it was running better than it did with the "new ones" ive tried techron fuel system cleaner, and it does make the car run better but doesn't fix the intermittent issue. But also thinking about injectors, what are the chances that two injectors go bad at the same time?

My question is could bad injector seals cause the problem Im having? (intermittent misfires in cyl 1-2) The seals on my injectors were basically gone and obviously looked original as well as the tips being full of soot and carbon.

Right now im starting to think it might be the post cat o2 sensors (to my knowledge they are original), as I have a code for them but in both banks, which is throwing me off, i have not gotten any misfires in bank 2. but i do have mixture codes in bank 1. which can point to multiple things. air or fuel related it seems to me that it is a definite bank 1 problem.

i do have a weird surge up and down in the rpms when i'm cruising at very low rpms 1.5k-2k but as i give it more throttle the surge goes away- but ive had this problem for a while. Can this be a a vacuum leak causing a misfire?

Im really just looking for some input or advice here, maybe someone else has ran into this issue before, looking through all the forums i haven't came across anything like the issue im having.
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Last edited by Dennyyv; 01-21-2023 at 09:57 PM..
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      01-23-2023, 09:44 PM   #2
Dennyyv
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So, I figured out my issue.

Driving the car trouble shooting it again today, I got a misfire in cyl 1-2 again. But soon after it started in cyl 3 as well. So the whole bank 1 is down. No other codes so I kept clearing and the misfire would not go away, as it usually would. I checked the codes and to my surprise I got the infamous

30bb- injector 1,2,3 or internal dme fault
(MOSFETS!!!)

So I took out the dme and inspected-
Intermittent misfires I was having on bank one, were a result of one of the injector mosfets for injector 1 not being correctly soldered- one of the feet on the mosfet was not soldered to the board but really just resting on there giving it some what of a connection, but intermittently coming off the board on say maybe a bump in the road or something. Usually if one mosfet on the bank is bad it causes the whole bank to misfire, but sometimes only the one right next to it. So I went ahead and used a heat gun with aluminum foil to make a funnel and reworked the mosfet to the best of my ability (as I gave away my hot air rework station and had to improvise)

I feel very stupid for not thinking of this in the beginning but - you live and you learn, I thought it couldn’t be the mosfets as I repaired them months ago. And it was very well for thousands of miles.

Goes to show, always double check your work.
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