Misfiring on only one bank (no other codes)

[monkishor]

Hello everyone,

Up until now I was mostly a "ghost reader" on this forum, but since my car has started going into limp mode recently I decided to register and ask your opinion on the symptoms my car has.

I will try to keep things short:

My car goes from time to time in limp mode, but ONLY at low rpms. First time it was actually idling, while parked and waiting for someone. The other times it did it only below 2000 rpm and usually while going downhill, below 30kph / 20mph without having the foot on the throttle. I never had limp mode come in at full throttle or while accelerating. Limp mode always goes away if I turn the engine off and then start it up again.

I have used Carly and pulled the following codes:

002B39 - Misfiring with shutdown cylinder 5
002B3A - Misfiring with shutdown cylinder 6
002B3B - Misfiring with shutdown cylinder 7
002B3C - Misfiring with shutdown cylinder 8
002B41 - Misfiring with shutdown more cylinders
002B57 - Engine emergency program activated
002796 - Engine emergency program activated

Car has never had ANY fault codes before, as I check it every 2-3 weeks and all of those came at the same time.

After getting these codes I immediately started thinking that it might be something that controls the whole driver / LH side bank (no. 2 I believe?), as they all came at the same time.
I thought that if it would have been a bad coil or a bad spark plug, it would have thrown a misfire on only one cylinder.

I went to BMW, as I needed to do the oil change anyway (only reason I'm doing it there is because the car has full BMW maintenance history... value ... bla bla bla). At BMW Monaco they did not even want to check the car because "we do not want to work on modified cars" - car has only an Eventuri filter and Sebring full exhaust. Its not the first time when they refuse to do "preventive work", as I have had arguments with them when asking to change the rod bearings in the past (ended up doing it at another dealership).

Anyway, I decided to take the car to another BMW dealership, where they were a bit confused as to why I would like to change the throttle actuators. However, after seeing their quote, I decided to just do the oil change and also change the spark plugs, since the car has around 108,000 kms (67k miles) and the last time they were changed it was at 60,000 kms. I hoped that this will clear the issue. The old spark plugs looked in good shape, for their age.
However, after driving the car home, the following day it went again in limp mode, with exactly the same error codes.

Not wanting to spend 1400 Euros on just parts to change the actuators without being sure this is the issue and after reading this entire thread, I have decided to troubleshoot the actuators by changing them from one bank to the other.

My friend uses Launch X431 Pros Mini as a diagnostic tool. Before starting the work, we ran a test with his tool and it came out with the following codes:

2B39 - Misfiring with shutdown cylinder 5
2B3A - Misfiring with shutdown cylinder 6
2B3B - Misfiring with shutdown cylinder 7
2B3C - Misfiring with shutdown cylinder 8
002B41 - Misfiring with shutdown more cylinders

It just did not mention the last two which Carly found about the emergency program

After taking everything apart, we realised the car had the original actuators in, based on the stamp.

Moving them from one bank to the other job took around 2 hours. I'm sure that with help it can be done a lot faster, but we really took our time.

After finishing the job, we put everything back together and reset the codes + we deleted the adaptations (but only the ones related to the throttle valves - all others were left "as is").
We went out with the car to test it and after few kilometers, it went again in limp mode, as expected.
HOWEVER, this time, when we read the codes it threw:

2B37 - Misfiring with shutdown cylinder 3
2B39 - Misfiring with shutdown cylinder 5
2B3A - Misfiring with shutdown cylinder 6
2B3B - Misfiring with shutdown cylinder 7
2B3C - Misfiring with shutdown cylinder 8

The exact same ones as before + cylinder 3, which never came up before.
I was expecting and hoping that the errors will just move from one bank to the other and then I would have just proceeded with ordering the actuators.

Our theory is that maybe, even if we erased the codes, somehow the car remembers them and now because all adaptations, besides the throttle valves are the same as before, the car just throws the same error, thinking it has the same problem as before and also points. I assume that it will still try to use all the other adaptations (ignition, O2, etc...) as it remembered with the potentially faulty actuator on bank 2, which will result in misfires on the same bank, until it re-adapts.

My friend was suggesting to keep driving it around and to erase the errors with Carly 2-3 more times, just to see if eventually it will shift to the other bank. I hope this will be the case, because at least I would have at least found the problem.

The next day, I took the car out again and it did not throw any errors. drove it till I got tired of it, trying to get it to limp again. HOWEVER, while in idle, while walking around the car, I've noticed that on the left side (somewhere behind the wheel) the exhaust sounds like is leaking. On the right side, it sounds normal. I am wondering if there might not be a leak, just before the O2 sensor, which could end up giving the sensor a faulty reading, and sometimes sending the engine in limp mode. But in this case, I would asume that if there would be an O2 sensor issue, it would throw an error related to that (either a bad mix of fuel & air, either directly an O2 sensor fault). Do you think O2 sensor on that bank could cause misfires on all cylinders at the same time ?

The car is also fluctuating a bit at idling while cold start, but this has always been the case since I bought the car, one year ago. (very little fluctuation)

Any opinions are welcome. I assume it would have to be a part which is governing / influencing the whole bank anyway.

Is it worth changing the actuators at this stage ? I see most people on other threads also always get an error related to the actuator when they fail. Mine never came up with that and I don't want to throw a large amount of money on it, just to realise that this was not the issue (even if for sure the actuators will go at one point).

I have heard from some other forums that a faulty injector on one of the cylinders could also be the culprit, resulting somehow in misfires on all cylinders on that bank, sending the engine in limp mode.

Sorry for the long post. Just trying to give as much info as possible.
Any opinion is welcome.

[Redd]

If you're hearing an exhaust leak then it's an exhaust leak.

[SilverSlug]

If you believe there may be an exhaust leak, you should find it and fix it before doing anything else just to eliminate that as a possibility, and perhaps/hopefully that will solve the issue.

Start with the headers and work down each section until the cats.

[Redd]

The graphite gaskets between the headers and front pipes are known to fail over time. Fairly common problem that can cause full bank misfires. Either that or O2 sensors.

[monkishor]

after driving it around some more, I still did not get any additional codes (did 100kms+).

However, I am now 99% sure my problem is because of the exhaust leak.
I have shot a video left vs right and I think it is clear that there is a leak on the LH bank, which is also the one who sent the car in limp mode. You can even smell exhaust gas next to the front left wheel.

My theory now is that because the car only went in limp mode when idling, or very low rpm, the the exhaust was getting false air, just before the O2 sensor, which sent it haywire. It never happened while in full throttle, because when there is so much gas, the pressure builds up and there is no more false air being drawn in the exhaust.

I have ordered the pre-cat gasket and I will try to exchange it once I get back from my holiday. I will keep you updated, but now I am quite confident I have found my problem. 10 euros for the gasket definitely beats 1500 for two throttle actuators

[amrazM]

Only put the genuine bmw gasket, the HJC gasket disintergrates quickly.

[monkishor]

Originally Posted by amrazM

Only put the genuine bmw gasket, the HJC gasket disintergrates quickly.

thanks for the heads up.
just ordered the OEM ones for 9 euros / piece + the screws.
hopefully will get them on the 10th of June

[monkishor]

Originally Posted by monkishor

thanks for the heads up.
just ordered the OEM ones for 9 euros / piece + the screws.
hopefully will get them on the 10th of June

just finished the repair...

when we got under the car and took off the exhaust we realised that there was no gasket on the left hand side...

after we put the oem gasket on and changed the one on the right side, the car has changed COMPLETELY. the sound is now smooth and linear... absolutely no more trembling when idling and the car now idles straight at 600rpm.
before there was a small fluctuation and it was always idling around 7-800rpm.

it all makes sense now... because probably the o2 sensor was getting a wrong reading and therefore was chocking the engine at idle, causing the "broken exhaust" sound, shaking and fluctuating idle.
I can now say that the problem was for sure coming from this.

I am absolutely shocked by how the engine runs now...

only took off the bolts from the exhaust and that allowed us to put in the new gasket without having to take off the exhaust.

we went full ghetto and literally did this on the side of the road and it took us around 1 hour in total. (it actually took us more time to put back the cover from underneath the engine than to actually change the gaskets)

I hope this will help some people having the same symptoms save some $$$ the repair ended up costing around 10 euros / 15 dollars for both gaskets + screws.