Misfiring On All Cylinders Only After Idling for a While

[sapote]

So I'm not sure which sensors I should be tracking, but I was messing around with the Schwaben scanner and recorded this.

O2 sensors pre-cat graph during normal idle:

I didn't followed this thread due to a time gap. But it's pretty useless to show a snap shot of the O2 voltages and the STFT. These data should be logged for at least 30 sec with one sample per second. Also include the LTFT. The MAF unit should be in gram/sec as LBS is too low resolution to tell a difference off bad vs good.

[CrookedCommie]

Did you ever resolve the issue?

[giOsaurus rEx]

So I'm not sure which sensors I should be tracking, but I was messing around with the Schwaben scanner and recorded this.

O2 sensors pre-cat graph during normal idle:


O2 sensors pre-cat graph during misfiring:


Few sensors during normal idle:


Few sensors during misfire:

[sapote]

So sounds like the pre-cat O2s need to be replaced then? Or should both pre-cat and post-cat O2 sensors be replaced?.

No, it's too early to think this is due to bad O2 sensor.
I suggest to use a diag tool, i.e. OBD Fusion, which can log all of the sensors data when the issue shows up. With the detail log data we can get to the root cause faster.

[Halftim3]

Get a leakdown test. Maybe your head gasket is only blown between cylinder 1 and 2 that's why it isn't misfiring that bad?
Not sure, but yes I believe it would misfire regardless of unplugging the MAF.
I didn't have milky oil or coolant in the cylinders when mine blew and it blew between cylinder 1 and 2, 2 and 3, 4 and 5, and 5 and 6. The gasket is thin in between the cylinders is the reason they blow, but mine only started having the CEL at 209k. It also had the CEL come on after idling a few minutes. I've done some research on it and on another forum someone blew as early as 50-60k miles.

[giOsaurus rEx]

Something causing the bad mixture of fuel/air, and unplug the MAF forced the DME to use opened-loop control (ignore the O2 sensor signals) and so engine ran richer but smooth.

So sounds like the pre-cat O2s need to be replaced then? Or should both pre-cat and post-cat O2 sensors be replaced?

Have you done a leakdown or compression test?A blown headgasket between the cylinders throws the same misfire CEL. It happens to some with lower mileage.

No I haven't. I'm talking to the shop whose done a lot of work for me about this. It isn't throwing any lights on the dash, just codes when I scan with a ECS Tuning Foxwell scanner. If it is the head gasket, wouldn't it misfire regardless of unplugging the MAF? My oil doesn't look milky and I'm not losing any coolant from the reservoir.

[Halftim3]

Have you done a leakdown or compression test?A blown headgasket between the cylinders throws the same misfire CEL. It happens to some with lower mileage.

[lemoose]

id rule out the egt. Youre probably only seeing a code for it due to a lean condition- which points back to what sapote says above

[sapote]

Car runs fine when I unplug the brand new MAF..

Something causing the bad mixture of fuel/air, and unplug the MAF forced the DME to use opened-loop control (ignore the O2 sensor signals) and so engine ran richer but smooth.

[giOsaurus rEx]

So I replaced the MAF and all the ignition coils with Bosch OE parts, but I'm still having the misfiring issue whenever it is idling for a while. Do I need to reset adaptations? Car runs fine when I unplug the brand new MAF. I got the same codes as the original post plus a few more this time when it was misfiring:

4F DME: Signal, exhaust-gas temperature sensor
AE DME: Fuel-system diagnosis, cyl 1-3
AF DME: Fuel-system diagnosis, cyl 4-6

Still no SES light on the dash when this is occurring. Can the EGT sensor be the cause of this or a combo of EGT/O2 sensors? I'm starting to think that I should ditch the MAF indefinitely lmao.

[Arith2]

Curious. Does anyone know what sensors alphaN uses? Is it everything except the MAF?

I think IAT is also part of the MAF harness.

The TPS and IAT mostly. You just rewire the IAT and put the sensor somewhere. Turner airboxs use a fitting that fits the M50 IAT.

[giOsaurus rEx]

Here’s the OE part to install into your existing housing .. $115.

https://www.fcpeuro.com/products/bmw...Lw_wcB#reviews

Awesome! I ended up ordering it from your link. Thank you!

[eacmen]

Curious. Does anyone know what sensors alphaN uses? Is it everything except the MAF?

I think IAT is also part of the MAF harness.

[repoman89]

So I think it's the MAF sensor. I unplugged it and drove around for about an hour. The car felt more responsive at lower RPM. I replicated the driving I did when we played Pokemon. Then I let it idle for 30 minutes. No misfiring and the throttle felt smooth like it should. I'm going to do the same test tomorrow to see if it wasn't just a fluke before ordering a $300 sensor 😮

Thanks for all the help!

Here’s the OE part to install into your existing housing .. $115.

https://www.fcpeuro.com/products/bmw-mass-air-flow-sensor-m5-z4-z3-m3-m6-0280218062?ads_cmpid=352576039&ads_adid=22972407319&ads_matchtype=&ads_network=g&ads_creative=85218275839&utm_term=&ads_targetid=pla-22190487637&utm_campaign=&utm_source=adwords&utm_medium=ppc&ttv=2&gclid=Cj0KCQjw38-DBhDpARIsADJ3kjnozwGuyvP8Mb03unDzk2gYmVfjiXAy4gG8CfVaeiHyDeyl5yFL_CAaAv12EALw_wcB#reviews

[giOsaurus rEx]

So I think it's the MAF sensor. I unplugged it and drove around for about an hour. The car felt more responsive at lower RPM. I replicated the driving I did when we played Pokemon. Then I let it idle for 30 minutes. No misfiring and the throttle felt smooth like it should. I'm going to do the same test tomorrow to see if it wasn't just a fluke before ordering a $300 sensor 😮

Thanks for all the help!