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      08-31-2022, 07:10 AM   #1
bruiser654
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F21 N13 Multiple Cylinder Misdire with no CEL

Hi all,


New to the forum but have been having issues with my F21 1 series for a little while now and cannot make head nor tail of the problem.

I am getting misfires on cylinders 1 and 4 mainly (Believe it is 1 and 4, I will confirm when I plug the car back in to ISTA).

It will misfire on idle but is definitely noticeably worse during the colder months (to the point the whole car will shake left to right from the misfire) but definitely misfires more as you are accelerating.

The misfire it much worse when holding RPM at between 2000-3000 and sometimes it ISTA will report cylinder 1 misfiring between 30-40 times within the space of 30-60 seconds.

Strange thing is, I have never once had a check engine light and with how sever the misfire is sometimes, this really surprised me but also means I am struggling to narrow down the issue.


I have already done/changed the below basic stuff to try and resolve or narrow down the cause but no joy so far:

- All spark plugs replaced
- All ignition coils replaced
- Misfire does not move when moving spark plugs about
- MAF sensor replaced
- Intake pipe replaced due to crack
- All breather pipes replaced, again due to cracks

I haven't replaced any other parts after this as I am at a loss of where to go from here and these were the cheaper bits to check.


I have read online the 116 and 118 Sport and M-Sport are known to blow the coil drive packs on the ECU but am reluctant to send it off for rebuild for 300 (I know it is not much but want to get more info first).

Someone also mentioned it could be a leaky or blocked injector but I would definitely expect an check engine light to show for this, especially when putting the car under heavy load (which I have tried, I have blasted it down the dual carriage way to try and trigger a code but still nothing).


Sorry if I have missed anything. Let me know if you need any more information and I will try my best to get it for you and I am also going to try and do some data logging in the next couple of days to help.


Thanks,
Brandon
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      08-31-2022, 09:08 AM   #2
IJO
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Quote:
Originally Posted by bruiser654 View Post
Hi all,


New to the forum but have been having issues with my F21 1 series for a little while now and cannot make head nor tail of the problem.

I am getting misfires on cylinders 1 and 4 mainly (Believe it is 1 and 4, I will confirm when I plug the car back in to ISTA).

It will misfire on idle but is definitely noticeably worse during the colder months (to the point the whole car will shake left to right from the misfire) but definitely misfires more as you are accelerating.

The misfire it much worse when holding RPM at between 2000-3000 and sometimes it ISTA will report cylinder 1 misfiring between 30-40 times within the space of 30-60 seconds.

Strange thing is, I have never once had a check engine light and with how sever the misfire is sometimes, this really surprised me but also means I am struggling to narrow down the issue.


I have already done/changed the below basic stuff to try and resolve or narrow down the cause but no joy so far:

- All spark plugs replaced
- All ignition coils replaced
- Misfire does not move when moving spark plugs about
- MAF sensor replaced
- Intake pipe replaced due to crack
- All breather pipes replaced, again due to cracks

I haven't replaced any other parts after this as I am at a loss of where to go from here and these were the cheaper bits to check.


I have read online the 116 and 118 Sport and M-Sport are known to blow the coil drive packs on the ECU but am reluctant to send it off for rebuild for 300 (I know it is not much but want to get more info first).

Someone also mentioned it could be a leaky or blocked injector but I would definitely expect an check engine light to show for this, especially when putting the car under heavy load (which I have tried, I have blasted it down the dual carriage way to try and trigger a code but still nothing).


Sorry if I have missed anything. Let me know if you need any more information and I will try my best to get it for you and I am also going to try and do some data logging in the next couple of days to help.
Thanks,
Brandon
I had something similar after changing the plugs but it was due to me not pushing the coil plugs on fully on two cylinders.

A bit of a rough idle and hesitation after a cold start seems quite common the N13b16 engine.

Does it settle down once warmed up or can you always feel it misfiring?
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      08-31-2022, 10:36 AM   #3
IJO
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Just had a thought.

When was the pre cat o2 sensor replaced? (recommended every 100k, or 85k in my case)

The DME detects misfires by looking at this sensors AFR reading on a per cylinder basis.

So if it detects rich pulse at the same time as these cylinders plugs are firing, it will log a misfire (unburned fuel causing a low AFR reading)

Perhaps it is the sensor that is sending an incorrect AFR reading - just out of spec enough to cause a misfire code, but not enough to be logged a faulty (because the other two cylinders are not misfiring)

If the DME sees a low AFR it will reduce the fuel quantity causing a weak misfire.

Might be worth changing it as its an easy job if you have a 22mm sensor socket.
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