[Klos]

2009 BMW 335XI

So recently I've been trying to diagnose my misfire on my N54, I have swapped coils, spark plugs, injectors, changed injector seals, decouplers. My car is still misfiring at idle and under 100% load for some reason and I don't know what to change or what to swap anymore. If anyone has had a similar problem please let me know, and yes I've literally swapped a set of new index 12 injectors into the car and the same problem persisted. It's not the injectors.

Car Is FBO, OEM Spark Plugs.

Injectors were coded each time I tested them

Smoke Test Completed, and no issues.

Compression Test, 175psi

Codes:
2C31(02 Sensor)
2C6B(O2 Sensor)
29D0 (Cylinder #4 Misfire)

No other codes.

Pleaseeee help me.

[Leanped]

When you swapped the injectors, did you code them in? Also, did you reset your adaptations?

Separately, it would be helpful to attach a log.

[Klos]

Originally Posted by Leanped

When you swapped the injectors, did you code them in? Also, did you reset your adaptations?

Separately, it would be helpful to attach a log.

Yes they were coded and could you be more specific on what adaptations should be reset.

[Dave92N54]

Check O2 voltages with inpa. Betting you needs downstreams.

[Klos]

Originally Posted by Dave92N54

Check O2 voltages with inpa. Betting you needs downstreams.

Could you elaborate, please?

[Wolf 335]

Originally Posted by Klos

2009 BMW 335XI

So recently I've been trying to diagnose my misfire on my N54, I have swapped coils, spark plugs, injectors, changed injector seals, decouplers. My car is still misfiring at idle and under 100% load for some reason and I don't know what to change or what to swap anymore. If anyone has had a similar problem please let me know, and yes I've literally swapped a set of new index 12 injectors into the car and the same problem persisted. It's not the injectors.

Car Is FBO, OEM Spark Plugs.

Injectors were coded each time I tested them

Smoke Test Completed, and no issues.

Compression Test, 175psi

Codes:
2C31(02 Sensor)
2C6B(O2 Sensor)
29D0 (Cylinder #4 Misfire)

No other codes.

Pleaseeee help me.

Having the exact same issue with cylinder 4 misfiring. If i push it hard it goes into limp mode (reduced power half check engine light)

I checked cylinder 4 spark plug and it was soaked with fuel.

Just picked up a new injector yesterday, hopefully it will resolve my issue.


In your case, you will need to check the O2 sensors, althougth i think O2 code is being triggered due to misfire and lean/rich runnign condition.
If you have ISTA or INPA software, you can find a few videos on youtube on how to check.

Have you double checked the injector harness for any wire damage?

[Dave92N54]

Originally Posted by Klos

Could you elaborate, please?

[jimmer411]

i struggled with misfires for about 2 years, just converted to B58 coils and iridium plugs gapped at .020. misfires are finally gone.

[Wolf 335]

Update on my issue:

Issue was in fact faulty injector.

Cylinder 4 injector was leaking. Spark plug was saturated with fuel.

Surprisingly decoupling element was missing. Last time this injector was touched was back in 2012 by the dealership. It was index 8. Am i suprised the dealership didn't put in the decoupling element, yes i am.

Anyways, I cleaned the injector bore and inspected for any damage or ovalization. All looked good. Popped in a new index 12 and all is good.

I been chasing a lean mixture code for bank 2 for over a year, and this finally solved it along with curing the limp mode.

[DocMike86]

Was having misfires on cylinder 4 on ‘13 335is with 32k. Swapped coils, plugs, verified 12’s. Still misfired at idle, but ran like a beast on track day. Had it walnut blasted a few weeks ago, problem solved.

[whyzee125]

Couple key things here:

- Index 12's, like any injectors, can go bad
- FBO should be running NGK plugs preferably 1 step colder. You may need to gap them down as low as .018 if you're running stock coils
- If you've tried everything else and you still have misfires while also throwing O2 codes, you should replace your O2 sensors