Rough Idle / M4 2018

[Moathir_Kamyani]

Hello guys,

I have been experiencing a rough idle. The issue started 2 days after I tuned my car to bootmod OTS stage 2 map.
I have then flashed back to stock and the issue is still there.
I have checked if there is any error codes or faults. Nothing is there (apart from the O2 sensor error code because of the catless DP).

My spark plugs are new (NGK 97506)
The ignition coils seem ok as there is no misfire according the computer check.

The mileage is 77000 km on my car.

Any idea what this could be?

[andrei.m4]

I was surprised when one of my coil failed and car not throw any code. I suggest you to buy a set of new coils. Oem or delphi both work great.( oem are delphi).

[Moathir_Kamyani]

I believe the computer check should show a misfire if the ignition coil is faulty

[andrei.m4]

I detected manually witch one is broken, i took out the electrical conection one by one with engine started. And still not throw any code with the coil connection out.
Rough idle was present ~30k miles, like a slight misfire time to time at idle. Than one coil faild totally. I decided replace all and that idle slight misfire disapeared.

[TopJimmy]

Pull plugs and re-check gaps are 0.023in to 0.021in. Also look for cracked ceramic insulators.

I've seen a new plug with a crack.
Also seen plug gaps close up a little after first use.