[histandards]

Ive been doing tons of reading on the subject and now im just confused on what i should try first. Im limited on time so id like to try and get it right the first time. Heres a quick synopsis of whats going on:

2010 335i with JB4 (map 1) and 63k miles.

It all started when i was doing a hard pull and near the top of the gear, i had a misfire and then a short while later a SES light. The car still seemed to drive fine after that. A few days later im getting really bad cold start misfires for the first 5 mins or so in the morning. Codes come back as 2C3E, 2CAB, 29D2, 29D0, 29D1, 29CC. Misfires in Bank 2 and the Bank 2 pre cat o2 sensor. After the car is warm it runs fine all the way to redline and feels normal. Maybe a little rough on the idle but its never been perfect. My gas mileage is about 16-17mpg city.

The car sat in a body shop for a couple weeks repairing hail damage (thanks Boston), and I expected the SES light to be on when i got it back. It wasnt, and the car ran perfect for about 500 miles (possibly because they unplugged the battery). Then one day it was back and now its hit or miss with whether or not it will misfire on a cold start. It doesnt struggle to start and the misfires and rough idle usually take about 1 minute to appear so that makes me think its not the injectors. The fact that the whole bank 2 is misfiring makes me think its not the plugs (although i did not change them when i put the tune in about 2500 miles ago). So that leaves the o2 sensor...

I currently have two pre-cat o2 sensors in hand and can replace them tomrorow morning but before I dive into that fun little task can anyone validate my logic here or tell me im wrong?

Thanks in advance!

[TrAcK TRaP]

spark plugs of course.. But while you are at 63K miles I would replace coils as well..

[histandards]

Originally Posted by N54CherryHill

spark plugs of course.. But while you are at 63K miles I would replace coils as well..

You think all three plugs in bank 2 went bad at once though? Also, if its plugs, why is it fine at high rpm, i normally think it would be the opposite.

I hear ya on the coils. might as well.

Thanks

[Mike@N54Tuning.com]

If the plugs haven 't been changed in the last 20-25K I would start there as they are due regardless. Next would be faulty coil packs or injectors, but the spark plugs are the simplest and cheapest of the possibilities.

Mike

[histandards]

Originally Posted by Mike@N54Tuning.com

If the plugs haven 't been changed in the last 20-25K I would start there as they are due regardless. Next would be faulty coil packs or injectors, but the spark plugs are the simplest and cheapest of the possibilities.

Mike

Thanks to both of you. Question, can bad plugs be causing the o2 sensor codes?

[idrift4wd]

COIL PACKS FIRST. THEN SPARK PLUGS THEN INJECTORS.

COILPACKS ARE THE EASIEST TO CHECK THEN SPARK PLUGS. Geez does anyone read the stickies.

[histandards]

ive read pretty much every misfire post on this and other forums. Im hoping that someone would explain their logic as to why its not the o2 sensor and why its the coils? how did three coil packs on the same side go bad at exactly the same time?

[idrift4wd]

Originally Posted by histandards

ive read pretty much every misfire post on this and other forums. Im hoping that someone would explain their logic as to why its not the o2 sensor and why its the coils? how did three coil packs on the same side go bad at exactly the same time?

o2 sensors codes are probably bad o2 sensors.

depending on the 3 cylinders that misfired if its in a full bank 1-2-3 or 4-5-6 could be injectors.

move coils packs around and see if it jumps around. then change your spark plugs. If you want you can swap plugs around also. This is always your first go to when dealing with misfires

[JDuke335i]

Originally Posted by histandards

ive read pretty much every misfire post on this and other forums. Im hoping that someone would explain their logic as to why its not the o2 sensor and why its the coils? how did three coil packs on the same side go bad at exactly the same time?

Change your plugs first. Delete all the codes and then see what codes come back

[Snypa]

Originally Posted by JDuke335i

Change your plugs first. Delete all the codes and then see what codes come back

+1

[Jklad]

Or, if it hasn't been done yet, replace all 6 plugs, all 6 coils, (cheap and easy to do) and since you have front O2s do that also and start off fresh. Idk how folks have time to keep swapping coils aroind multiple times, then plugs, then letting things cool off, testing, tearing down the cowls every time (yeah I know it takes 20 min but still lol!) etc.

[histandards]

thanks guys. So this morning i swapped the bank 1 coils with the bank 2. Cleared the codes now to wait and see if the misfires move. I started and ran it for a bit, it was idling rough but it didnt seem to be misfiring. I only did the coils because im waiting for the plugs to arrive in the mail. that will be next since theyre due anyway.

[Riceball777]

I just bright my 335i with 92,000 miles. It was bone stock and it was fine. Was I install full bot ons right away with a jb4 and it will miss fire every single time I went into boost. My spark plugs and coil were new. I walnut blasted and cleaned my intake valves it it solved my issues 100%. My intake valves were so gunked up I'm surprised the car even ran.

[histandards]

someone else also suggested dirty valves. ill definitely add it to my list of possibilities.

Update: my battery died sunday morning for some reason so I changed it out and of course the misfires and codes are gone for now. I say for now because they went away for about 500 miles when I got my car out of the body shop last month. I expect them to return soon, which also makes me think its something electronic like the o2 sensor versus mechanical like a leaking injector.

[histandards]

Update: so the misfires didn't follow the coils so I changed out the spark plugs and when I got to cylinder 5 I found a nice gunked up spark plug blacker than night. It smelled like fresh gas and there was carbon deposit stuck between the electrode and the ground. So I'm guessing that injector is bad. I swapped the plugs and it's currently running fine but I'm definitely replacing that injector next, then probably that spark plug again. Lol

[mikewills]

Thank you for keeping us updated. Now, get that injector swapped ASAP.

[cstmx_ryder]

I'd like to know more about the O2 sensors and how it plays into this misfiring deal....I'm currently experiencing similar issues, see my thread on here.

I'm down to injectors as my last option, until hearing about the O2 sensors, which I'd never thought about.....

TIA

[histandards]

Originally Posted by cstmx_ryder

I'd like to know more about the O2 sensors and how it plays into this misfiring deal....I'm currently experiencing similar issues, see my thread on here.

I'm down to injectors as my last option, until hearing about the O2 sensors, which I'd never thought about.....

TIA

My opinion, at least in my case is that the misfire in Cyl 5 was caused by poor ignition, so the 02 sensor readings from that bank were probably looking way out of range making the computer think that the 02 was defective hence throwing the code. something like that.

In your case, what did you plugs look like when you pulled them? also check the SN on your injector to make sure they are not the old ones that were recalled. Mine were the newer version and one still failed.

[Tech567]

Remove plugs and observe first. If they're fouled or smell like gas, your injectors are leaking...common issue that no one is mentioning. It's highly unlikely that that many coils are going bad at once. If plugs are fine, swap coils from bank 1 and 2 with each other. See if misfires migrate. If they do, than you got coil issues on your hands. Thats are diagnosis procedure in the shop (BMW) PM me if you need better assistance.

[N54Society]

Originally Posted by Tech567

Remove plugs and observe first. If they're fouled or smell like gas, your injectors are leaking...common issue that no one is mentioning. It's highly unlikely that that many coils are going bad at once. If plugs are fine, swap coils from bank 1 and 2 with each other. See if misfires migrate. If they do, than you got coil issues on your hands. Thats are diagnosis procedure in the shop (BMW) PM me if you need better assistance.

Do you have to switch from bank one to bank two to see if the misfire on the coils follows? Bank 1 = 1,2,3 and Bank 2= 4,5,6 right? So if the misfire is on cyl 3, can he just throw it in cyl 1, clear the codes and retest or does it need to go into one of the slots in bank 2?

[Tech567]

Originally Posted by vbp6us

Do you have to switch from bank one to bank two to see if the misfire on the coils follows? Bank 1 = 1,2,3 and Bank 2= 4,5,6 right? So if the misfire is on cyl 3, can he just throw it in cyl 1, clear the codes and retest or does it need to go into one of the slots in bank 2?

If he's just misfiring in 1 cyl he can swap it wherever he want. But sometimes a misfire in one cylinder can cause the surrounding cylinders to register a misfire.

[Abax335]

02 sensors don't really fail like that. They can be fouled or have heater cicuits that fail but generally do not cause a misfire.... I've seen way to many people codemn 02 sensors for doing tjere jon and monitoring the air fuel. In this case and many others its reading correctly. It sees the extra fuel being dumped from the leaking injector. This injector is also the long crank most likely. Make sure you replace the injectors accordingly based in your index #