BMW M5 Forum and M6 Forums banner

1 - 4 of 4 Posts

·
Registered
Joined
·
58 Posts
Discussion Starter · #1 ·
taclking maintenance today, i replaced the battery in the m5. everything went fine, until i start her up. she sputters and dies. i'm freaking out, man. do it a few more times until it idles rather roughly. i take her out for a drive, she pulls fine to redline, no smoke or drama. whenever i come to a stop she dies. gets better after a while, i put about 20 miles on her and she seems to be running fine now. was this a case of the DME needing to adapt? i'd be surprised everything was just wiped clean like that. checked all my vac lines and such, everything looks fine. weird, that's all.
 

·
Registered
Joined
·
1,298 Posts
It sometimes depends how long the ecu is without power for...
The idle speed control is adaptive & has to relearn the friction
characteristics of the engine once the stored data is wiped.

This can take a fair few miles....
All sorted now by the sounds of it though ! :cheers:


Alan.
 

·
Registered
Joined
·
2,415 Posts
Your's sounds like a particularly harsh "re-learning", but as it appears be ok now I think you'll be ok.

Whenever I've done mine, I don't get the spluttering and dying quite as bad as you did, but I'd like to warn new owners about one little trick the car will do.

When after a disconnect whe the DME is in learning mode, the computer has trouble working out just where idle will be. If the engine is mildly revved or running at say over 2000rpm and the the throttle lifted off completely, you will see the revs drop to below 900 where you'd expect it to recover. But as it's still recalibrating, you'll often see the engine dip as low as 400rpm, where it stutters, momentarily chokes before the ECU panics and blips back to 950-1100rpm before settling again.

The danger is if you are out on a drive when this happens, most often decelerating for a roundabout or junction. If when you are braking and clutch is down whilst changing gear the engine drops to that "unlearnt" 400/500rpm, then if in that exact moment you make a moderate turn of wheel (suddenly loading the power steering) it is enough to stall the engine, at which point you have no power steering or brakes. Worse than that, you won't be expecting it. Not fun.

I just thought I'd stick this on the Internets so that everyone, especially newbies to the car, are aware. I nearly crashed in 2002 the first time I experienced this phenomenon dropping from 3rd to 2nd whist preparing to gun off down a sliproad whilst deliberately going for a 25 mile driver to help the ECU learn again!

You never know, it might one day save an M5!

Regards

Ivan
 
  • Like
Reactions: Lantz and davidoli

·
Registered
Joined
·
58 Posts
Discussion Starter · #4 ·
thanks for the insight ivan. i put a few more miles on her today after washing her and the funny thing is, the car has a solid idle and has yet to die. i guess i've never seen DME "re-learning" in such a small scale of no-power time.
 
1 - 4 of 4 Posts
Top