Rough Idling (hunting)

[ArieArie]

2018 F80 m3, stock.

The engine's idle is irregular.
It sounds like it is hunting in cycles of approximately 10 seconds.
when it's on the low range of RPM, around 650, it grunts a bit at if a cylinder is missing.

Any idea what this could be?


Thanks!

A

here's a graph of the car idling for about 40 seconds.

[Wanted_M]

Easy checks that you can do.
1. Check DME codes with Bimmercode or ISTA. Clear all codes, run car and see what comes back.
2. Check all your fluid levels (intercooler reservoir & main coolant reservoir) to make sure you don't have a leak.
3. Visually check plastic intercooler piping for cracks.
4. Clean MAF sensors.
5. Check air filters, replace if filters are dirty.

If all that checks out and car still idling funky. It could be a bad coil or fouled plug, check the codes and see which cylinder is misfiring, swap that coil to another cylinder and see if it follows. Hope this helps, good luck.

[GuyLedouche]

Try taking the oil cap off while the engine is running. Mine was doing the same thing and would smooth out when I pulled the cap. PCV was failed.