F10 M5 - Misfire when cold - injectors?

[ajm55]

My instinct says you're correct, but I have no meaningful insights. I applaud you for your methodical approach to trouble shooting. I hope you get it sorted soon

[TinCanSailor]

Really the next level would be checking continuity in specific pins in the cable harness, chafed/bare wires grounding out/shorting etc... It might be worth looking for TSB's that describe similar conditions to help narrow the test and inspection points.

[Kamate]

Are the dme interchangeable? If it is, swap it around and see if you still have the same misfire.

[magsmagsmags]

Thank you all

Wiring diagrams are next on my list but I’m absolutely awful at reading them. I might just get an auto electrician out for a couple of hours see if they can crack it. At the very least if no fix they can rule out the wiring and electrical system

I’ve no idea if the DMEs are interchangeable. I imagine the answer is technically yes. Same part. But they’ll be programmed for each bank with appropriate firing order. So really, no (not without reflashing)

FWIW I tried fitting and coding a new battery today. Cylinder 4 misfire briefly reappeared after the switch. Again hinting to me it’s electrical but no closer to what

Appreciate everyone’s help so far. I’ll keep this up to date for future readers to troubleshoot when I eventually get it

[magsmagsmags]

Hi folks

Just wanted to update this to help others as there's nothing worse than trying to search for similar threads only to find the solution wasn't posted.

So long story short - The issue was a bad map!

I found out you can swap the DME's, so did just that and swapped bank 1 for 2. The misfire followed. A bad map still wasn't what I suspected, so I paid to have my DME cloned to a known working one and fitted that. Still no fix.

The place I went with then sent me another just to be sure - still no dice.

After that I figured that is the only thing it could possibly be, so flashed MHD onto it (was running a generic stage 2 from some remap place - you know the ones, your local guy! from the previous owner beforehand).

Straight away it's a different car, it sounds different, idles different, the misfire has gone and holy **** it's terrifying to drive. Made me realise how bad the previous map was.

So we're all good! Thank you everyone for your help

Hope this helps someone else in future

[ajm55]

Awesome that you resolved this. Well done. I would've thought that the files for the two DMEs are mirrored. If that's correct, then I infer that your DMEs had different files loaded onto them - one good and one bad - which would be rather curious

[kelvin12382003]

Originally Posted by magsmagsmags

Still chasing this if anyones got any other bright ideas. I’m 100% convinced the issue is electrical at this point. But not sure what or where

Hello I am having the same issue !! Do I need to get a new map ?

I am really lost

Cheers
Kelvin