M4 Rough Idle/Dropping Revs with Stary/Stop

[simmsy93]

Hi all,

Recently became an owner of a '17 M4 competition which I am delighted with after wanting one for years!

I have noticed driving it recently that the idle is a little rough but having not driven another M4 not sure how normal this is. If I have start stop on it also either drops the revs when starting up unless I give it a bit of throttle and can sometimes throw itself into neutral and makes me manually start the car!

I have BM3 on it with the trans flash but taking this off seemed to make no difference. I am unsure of the issue as when giving it the beans it absolutely flies and doesn't give me any error codes.

It came with a warranty but looking at reviews they never pay out and don't want to take it to my mechanic without an idea of what it could be.

So far I have possible options down to;

Starter motor
Dirty sparks
Possible coil pack issue

Any ideas or similar issues would greatly help.

[t5pilot]

A lumpy idle can be quite common. Check in the BM3 interface if cold start has been disabled, it's usually a likely cause of what you describe, even with the engine up to normal temperature.
You do have the option to raise your idle revs if it's causing an issue for you.
It should have had new plugs by now. Next time they're done get the NGK ones, they helped mine a little with the same issue. But I've had stop/start coded off by default for years, as it's temperamental anyway, as well as a pita.