Occassional misfire

[JoepM5]

Hi all,

I have encountered a misfiring issue with the M5 recently.

First time was over 1 month ago (c. 500 miles), it suddently started misfiring when engine was cold and driving in traffic (no pulls or anything). Got a CEL/Drivetrain malfunction but quickly restarted the car at the traffic light and thereafter the CEL was gone but still light misfiring. When I got home I didn't get any codes with my (basic) scanner.

Watched it closely thereafter but in the weeks following (c. 500 miles) no misfiring whatsoever, until it was back last week. Now I get the following codes:

152D08 : super knocking
152108 : super knocking injection cut cylinder 1

Symptoms/context:
- Spark plugs & coils were changed c. 2500 miles ago (along with injectors, high pressure fuel pumps, lambda sensors and software update)
- Have quicky replaced the coil on cylinder #1 again, didn't dare to do the spark plug myself but this hasn't had any impact
- The misfires are not consistent, not every trip and not always at the same moment. Only when accelerating, but not always
- I run 102 octane petrol
- Car is completely stock

Any one any ideas?

Thanks a lot!

Best,
Joep

[M5Rick]

Originally Posted by JoepM5

Hi all,

I have encountered a misfiring issue with the M5 recently.

First time was over 1 month ago (c. 500 miles), it suddently started misfiring when engine was cold and driving in traffic (no pulls or anything). Got a CEL/Drivetrain malfunction but quickly restarted the car at the traffic light and thereafter the CEL was gone but still light misfiring. When I got home I didn't get any codes with my (basic) scanner.

Watched it closely thereafter but in the weeks following (c. 500 miles) no misfiring whatsoever, until it was back last week. Now I get the following codes:

152D08 : super knocking
152108 : super knocking injection cut cylinder 1

- Spark plugs & coils were changed c. 2500 miles ago (along with injectors, high pressure fuel pumps, lambda sensors and software update)
- Have quicky replaced the coil on cylinder #1 again, didn't dare to do the spark plug myself but this hasn't had any impact
- The misfires are not consistent, not every trip and not always at the same moment. Only when accelerating, but not always
- I run 102 octane petrol
- Car is completely stock

Any one any ideas?

Thanks a lot!

Best,
Joep

I guess it's Aral 102,just a thought but try with 98/99 RON and see how it is then.

[JoepM5]

Hi Rick,

No, I’m in NL so its not Aral. It is a local pump that provides the 102.

I have run on 102 for 7k miles without issues and recently also had a tank of 95 since nothing else available, it also happened then. So I don’t think it is the fuel.

Best,
Joep

[M5Rick]

It could be a failing spark plug, unlikely on new plugs but not unknown for it to happen, that's why I had a plug change at a BMW dealer with the 2 year parts/labour guarantee.

[JoepM5]

Hi guys,

As an update - the car has been with the shop for a few weeks now. They had quite a backlog so took a while before they could start working on it.

Status is that mechanically everything seems OK (compression, cylinder leak testing, etc.) but when the engine warms up the misfiring starts. Also checked spark plugs, coil packs, etc. but that didn't solve it yet. They are now planning to switch the DMUs to see whether the issue also changes with it.

Anyone else suggestions what it could be?

Thanks a lot!

Best,
Joep

[JoepM5]

Hi all,

One more update - it has been fixed again

Turned about to be some wiring that was not 100% anymore (mass).

Best,
Joep

[M5_Raz]

Do you know what wiring?

Sorry I didn't see this thread earlier to contribute. I had a similar issue with a loose DME ground wire. I know of someone else on here who's has the same.

[JoepM5]

Hi Raz,

Was somewhere in the wiring harness, not close to the DME (what I understood from the shop).

Mass/ground wires seem to be a misfiring cause, they checked all ground wires on mine

Best,
Joep

[M5_Raz]

Interesting, glad it was fixed and the beast is back to normal!