Misfire + Rough Idle…then gone

sea_m2c · 06-30-2021, 08:20 PM

Last week I was on the track for the first time in my M2C (not the first time on track ever).

I was on maybe lap 4 of my 3rd session, heading down the back straight at about 140mph and around 7000k RPMs. Suddenly right before my braking zone at the end of the straight my car threw a Drivetrain Malfunction error and as I slowed down I could feel a rough idle.

I limped the car off of the track, got out of the car and confirmed a very rough idle. The car sounded close to being cammed. I shut down the car and when I put it back into accessory mode the drivetrain error was gone. I scanned for codes and got a Misfire on Cyl 6 shadow code….but the car seemed to be fine on its own. I did not clear codes and the error message had gone away on it's own.

When I started her up, she was running just like normal. I took it out for a couple of minutes outside of the paddock and no issues. Took her back out for a few more 50-75% laps, no issues.

Any idea what could have caused not only the Cyl 6 misfire but the fact that it persisted and was rough idling until I shut the car down? I've had misfires on other BMWs that were being push, and they've sometimes gone into limp mode, but we're never accompanied with a sustained rough idle that then disappeared after a shutdown/restart.

I'm wondering if there was knock detected and the car shut down Cyl 6 as a safety measure until it could be restarted? Or perhaps the issue with the stock heat exchanger shooting coolant into Cyl 6?

Thanks in advance for any insight.

workerONE · 07-01-2021, 02:57 AM

I had two cylinder misfires on my stage 3 GTI within a few weeks of each other. Each time I got a misfire the car put a light on the dash and the power was reduced immediately and it shuttered at lower rpm. When I turned the car off and on again it drove fine. I had been getting lazy and filling up at any gas station. The mechanic (who's pretty good) didn't find anything wrong with it but they recommended that I only use Shell or Chevron and I haven't had any issues since then, about 10 months.

Enabled · 07-02-2021, 10:57 AM

The misfire and rough idle is a consequence of the ecu shutting down the cylinder for its own protection. There are many reasons why a cylinder would shut down. It's normal for it to get back to normal after restart.

I would scan it with a BMW manufacturer code capable scanner (not P codes!) if you haven't cleared the codes already, and then inspect the spark plug.
If it happens again, move the ignition coil to another cylinder and see if it follows.

chiefsubjugator · 07-04-2021, 03:11 PM

Same thing happened to me at Sonoma coming out of turn 10. Got the drivetrain error, with corresponding loss of power and rough idle. Pulled into the pits, turned the car off/on and drove it around a bit. Plugged in a code reader and saw the P0306 code. Did one more session after that and took it to BMW the next week.

The dealer verified that I had a cylinder 6 misfire around 7K rpm. They ran some tests but were unable to reproduce. They did run a 'fuel quality test plan' which reported back 'mid range fuel'. I'm not sure how conclusive that is though as I had emptied/filled the tank by then just by virtue of driving back home.

Anyway to make a long story short, I've been to Sonoma two more times since then, ran the car just as hard and haven't had an issues. I'm hoping it was a one-time thing.

The one thing I've done since then is make sure the tank is full or at least above halfway full when I'm running on track. Not sure if it really makes a difference but at least at Sonoma it's not really much of a hassle (the gas station is right by the track exit).

sea_m2c · 07-05-2021, 04:43 PM

Quote:

Originally Posted by chiefsubjugator

Same thing happened to me at Sonoma coming out of turn 10. Got the drivetrain error, with corresponding loss of power and rough idle. Pulled into the pits, turned the car off/on and drove it around a bit. Plugged in a code reader and saw the P0306 code. Did one more session after that and took it to BMW the next week.

The dealer verified that I had a cylinder 6 misfire around 7K rpm. They ran some tests but were unable to reproduce. They did run a 'fuel quality test plan' which reported back 'mid range fuel'. I'm not sure how conclusive that is though as I had emptied/filled the tank by then just by virtue of driving back home.

Anyway to make a long story short, I've been to Sonoma two more times since then, ran the car just as hard and haven't had an issues. I'm hoping it was a one-time thing.

The one thing I've done since then is make sure the tank is full or at least above halfway full when I'm running on track. Not sure if it really makes a difference but at least at Sonoma it's not really much of a hassle (the gas station is right by the track exit).

I appreciate this response, it sounds identical to what happened to me - which makes me feel a little better.

Good tip on keeping the fuel above 1/2 tank, I was probably just below 1/2 at this point in the day. I was on the main straight though, so not exactly where I'd expect a low tank fuel level issue to happen…but I've seen weirder things lol.

Thanks again for your response!

iam2slow · 09-01-2021, 04:31 PM

Same thing happened to me at Sonoma last weekend. Second lap of my last session approaching T2, the car went into limp mode and threw a drivetrain malfunction code. I limped back to the pits sounding like a cammed corvette 🤣I turned the car off, checked for codes, and found a misfire in cylinder 5. After clearing the code, I turned the car on and it sounded normal again like nothing happened. Drove home and drove around the next day no issues whatsoever. FYI, the car is a MY 2017 stock tune with 15,000 miles, and I had exactly 1\2 tank of gas when this happened. Idk if the heat could've been an issue, but it was around 95F that day with slight smoke in the air (California fires). First time this happened to the car after 6 trackdays.

Rumbloki · 09-02-2021, 11:19 AM

Got misfire on cylinder 6 a couple of weeks ago while driving on the street. No limp mode. Cleared it. Later ran 6 laps of Auto-x on 1/6 of a tank with no issues. Has not returned.

I only buy Shell gas. 4k miles on the car.

Mar1usz · 11-25-2021, 01:47 PM

Don't mean to bump an old thread but I just had the same thing happen to me, 2021 M2C with 2,700miles. I was doing 3rd-4th gear pulls when the drivetrain malfunction notification displayed on idrive and check engine light came on. I pulled off the highway and had a very rough idle (felt like I was sitting in a massage seat). Shut the car off and turned it back on and it appears to be back to 100%. MyBMW says 3 Gals of fuel left in the tank (just under 1/4).

Anyone have the issue come back?

Mar1usz · 12-22-2021, 02:16 PM

Update: I read the shadow codes stored in the ECU and there was a misfire on cylinder #1. A few days later the Check engine light came back on but this time it stayed on.

Took the car to the dealer and they replaced the spark plug and coil pack on cyl #1, appears to be back to normal now.

06-30-2021, 08:20 PM	#1
sea_m2c Private First Class 82 Rep 170 Posts Drives: 2019 M2C - 6MT Join Date: Oct 2017 Location: Seattle iTrader: (0)	Last week I was on the track for the first time in my M2C (not the first time on track ever). I was on maybe lap 4 of my 3rd session, heading down the back straight at about 140mph and around 7000k RPMs. Suddenly right before my braking zone at the end of the straight my car threw a Drivetrain Malfunction error and as I slowed down I could feel a rough idle. I limped the car off of the track, got out of the car and confirmed a very rough idle. The car sounded close to being cammed. I shut down the car and when I put it back into accessory mode the drivetrain error was gone. I scanned for codes and got a Misfire on Cyl 6 shadow code….but the car seemed to be fine on its own. I did not clear codes and the error message had gone away on it's own. When I started her up, she was running just like normal. I took it out for a couple of minutes outside of the paddock and no issues. Took her back out for a few more 50-75% laps, no issues. Any idea what could have caused not only the Cyl 6 misfire but the fact that it persisted and was rough idling until I shut the car down? I've had misfires on other BMWs that were being push, and they've sometimes gone into limp mode, but we're never accompanied with a sustained rough idle that then disappeared after a shutdown/restart. I'm wondering if there was knock detected and the car shut down Cyl 6 as a safety measure until it could be restarted? Or perhaps the issue with the stock heat exchanger shooting coolant into Cyl 6? Thanks in advance for any insight. __________________ Current: 2019 M2 Comp, Coilovers, Camber Plates, Rogue SSK, AA Single MP, BM3 Stg 1 Sold: 2015 M235i RWD, MHD Stage 2, FBO, MPE, XHP, HPD5Evo \| IG @sea_m235i
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07-01-2021, 02:57 AM	#2
workerONE Private 70 Rep 71 Posts Drives: M2C, GTI Stage 3 Join Date: Dec 2020 Location: Coachella Valley, CA iTrader: (0)	I had two cylinder misfires on my stage 3 GTI within a few weeks of each other. Each time I got a misfire the car put a light on the dash and the power was reduced immediately and it shuttered at lower rpm. When I turned the car off and on again it drove fine. I had been getting lazy and filling up at any gas station. The mechanic (who's pretty good) didn't find anything wrong with it but they recommended that I only use Shell or Chevron and I haven't had any issues since then, about 10 months.
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07-02-2021, 10:57 AM	#3
Enabled Lieutenant Colonel 1407 Rep 1,800 Posts Drives: 328xd Wagon, M2 Competition Join Date: Jun 2018 Location: Houston iTrader: (0)	The misfire and rough idle is a consequence of the ecu shutting down the cylinder for its own protection. There are many reasons why a cylinder would shut down. It's normal for it to get back to normal after restart. I would scan it with a BMW manufacturer code capable scanner (not P codes!) if you haven't cleared the codes already, and then inspect the spark plug. If it happens again, move the ignition coil to another cylinder and see if it follows. __________________ -2014 328d Wagon, 8HP. Self-tuned, 270hp/430ft-lbs. -2019 M2 Competition MT, Alpine White. Self-tuned 560hp -2016 Mini Cooper S, MT. Many plans. Others: -E36 328is. 2000 Z3 Roady. 2003 VW Jetta TDI Manual. Estoril Z3M Coupe.
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07-04-2021, 03:11 PM	#4
chiefsubjugator Private First Class 91 Rep 135 Posts Drives: 2020 M2C 6MT LBB Join Date: Dec 2017 Location: Northern California iTrader: (0)	Same thing happened to me at Sonoma coming out of turn 10. Got the drivetrain error, with corresponding loss of power and rough idle. Pulled into the pits, turned the car off/on and drove it around a bit. Plugged in a code reader and saw the P0306 code. Did one more session after that and took it to BMW the next week. The dealer verified that I had a cylinder 6 misfire around 7K rpm. They ran some tests but were unable to reproduce. They did run a 'fuel quality test plan' which reported back 'mid range fuel'. I'm not sure how conclusive that is though as I had emptied/filled the tank by then just by virtue of driving back home. Anyway to make a long story short, I've been to Sonoma two more times since then, ran the car just as hard and haven't had an issues. I'm hoping it was a one-time thing. The one thing I've done since then is make sure the tank is full or at least above halfway full when I'm running on track. Not sure if it really makes a difference but at least at Sonoma it's not really much of a hassle (the gas station is right by the track exit).
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09-01-2021, 04:31 PM	#6
iam2slow Private 79 Rep 72 Posts Drives: 2017 M2 Join Date: Nov 2020 Location: Bay Area, CA iTrader: (2)	Same thing happened to me at Sonoma last weekend. Second lap of my last session approaching T2, the car went into limp mode and threw a drivetrain malfunction code. I limped back to the pits sounding like a cammed corvette 🤣I turned the car off, checked for codes, and found a misfire in cylinder 5. After clearing the code, I turned the car on and it sounded normal again like nothing happened. Drove home and drove around the next day no issues whatsoever. FYI, the car is a MY 2017 stock tune with 15,000 miles, and I had exactly 1\2 tank of gas when this happened. Idk if the heat could've been an issue, but it was around 95F that day with slight smoke in the air (California fires). First time this happened to the car after 6 trackdays.
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09-02-2021, 11:19 AM	#7
Rumbloki Second Lieutenant 176 Rep 201 Posts Drives: Faster than most Join Date: Oct 2020 Location: ATX iTrader: (0)	Got misfire on cylinder 6 a couple of weeks ago while driving on the street. No limp mode. Cleared it. Later ran 6 laps of Auto-x on 1/6 of a tank with no issues. Has not returned. I only buy Shell gas. 4k miles on the car. __________________ 2021 M2C, HS, 6MT, ZED, 763M w/spinners, AA single, AA axle back, Turner High Kick, Turner shifter support, M pedals, honeycomb reflector delete, BC Racing DS series
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11-25-2021, 01:47 PM	#8
Mar1usz New Member 15 Rep 11 Posts Drives: 2021 M2C Join Date: Jun 2021 Location: Brooklyn NY iTrader: (0)	Don't mean to bump an old thread but I just had the same thing happen to me, 2021 M2C with 2,700miles. I was doing 3rd-4th gear pulls when the drivetrain malfunction notification displayed on idrive and check engine light came on. I pulled off the highway and had a very rough idle (felt like I was sitting in a massage seat). Shut the car off and turned it back on and it appears to be back to 100%. MyBMW says 3 Gals of fuel left in the tank (just under 1/4). Anyone have the issue come back?
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12-22-2021, 02:16 PM	#9
Mar1usz New Member 15 Rep 11 Posts Drives: 2021 M2C Join Date: Jun 2021 Location: Brooklyn NY iTrader: (0)	Update: I read the shadow codes stored in the ECU and there was a misfire on cylinder #1. A few days later the Check engine light came back on but this time it stayed on. Took the car to the dealer and they replaced the spark plug and coil pack on cyl #1, appears to be back to normal now.
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