BMW G30 540i (B58) Misfire, Running Horribly

[Frankie M]

Hello, I have a 2018 G30 540i with 17k miles and have been battling some misfire (running rich) for the past 3 months. I've been back and forth with the dealership, and they have still not been able to fix it. First they tried spark plugs, which didn't fix the misfire. Then they tried reflashing my DME with the stock B58 tune to try to reset the values. This worked, but only for a day or so and then the car went back to misfiring and running rich. The previous owner of the car used JB4 and the dealer was able to trace it and said my DME (ecu) was bad because of it, so i bought a new one from them. They put it in and this worked for about 3 days, it ran perfectly (confirming the problem is not mechanical) until this mornings cold start where it went back to how it used to be. Misfiring like crazy and black smoke coming out of the exhaust. At this point I'm not sure what it is, but am almost certain its electrical. As of right now I'm not sure what to do as the dealer seems to be no help.

[gery11]

Hello Frankie,

It can be many things, wiring, ECU, wrong spark plugs, coils, camshaft sensor etc...
A good garage can maybe use an oscilloscope in the troubleshooting helping you to find it out.

Have you checked if you get any error codes?

Bst

[Car420parts]

Hello, I feel like I have a very similar problem with my BMW have you gotten an further on finding out what’s wrong?

[shogun]

My Cars: BMW

Please complete your profile.

What we need to diagnose your issue :
There are a bunch of really good techs, bimmerheads, and helpful people at this forum. But if you don't provide pertinent data, no one can help you diagnose the issue you're having.

First, we need the year, and model. The mileage is often helpful. sometimes the transmission, and certainly what aftermarket equipment you might have which might in any way be involved. That means, if you've got an electrical or starting issue, we need to know if you have a big stereo, or an alarm system!

Please, help the readers and responders help you. Without data, we're guessing.

Telling us the symptoms, and when they happen, is a really good idea. If you hear a noise, tell us when it happens: cold, hot, at low speed, under acceleration, etc. Tell us where the noise is coming from, and preferably post a video, with sound. If you have warning lights on, whether you think they're related or not, tell us.

[Car420parts]

Hello

I have a 2017 BMW 540i with 35k miles, when the car is started the EML is on and the car misfires and really running rich a lot of smoke out the back , managed to plug it into some diagnostics equipment but it was quite basic and told me I had a misfire on cylinders 4 5 6. I feel like my problem is very similar to the situation above, I managed to clear the light and try the car again and it ran steady for a period of time and the light come on again IÂ’ve had it running a couple of times and itÂ’s always the same 70% misfire and only a little running clean, IÂ’ve searched loads of websites trying to find someone with this problem and can only find this. any suggestions would be appreciated

[pbonsalb]

4,5 and 6 is Bank 2. If the problem is affecting an entire bank, I would first suspect the things that affect an entire bank, like the 02 for that bank. I’d start with the primary, but have read that a distorted secondary can eventually affect the fueling.

You could try swapping the primary 02 to see if the problem moves to the other bank after a bit of driving. That is free — just your time. I would not throw parts at the car and hope. Instead, diagnose and test.

The smart thing would be to borrow a high level scan tool.