Hi everyone,

I’m having a strange issue with my BMW F20 116i 2012 (N13 engine) and I’m trying to figure out the cause.

The problem appears only in a specific condition:
After the car sits for about 4–6 hours (so not fully cold, but not warm either – kind of a semi-cold start).

At startup, the engine revs higher as expected. As the RPM starts to drop, I can hear a brief wastegate rattle. Immediately after that, the RPM fluctuates slightly and settles around ~700 rpm, where I notice a small vibration/shake.

After about 30–60 seconds or once I start driving, the engine becomes perfectly smooth with no vibration at all.

Important notes:

• Cold starts (after overnight) are perfect

• Fully warm restarts are also perfect

• The issue only appears in this “semi-cold” condition

Work already done:

• timing chain kit replaced

• injectors replaced

• ignition coils and spark plugs replaced

• MAF sensor replaced

• MAP sensor replaced

• lambda (O2) sensor replaced

• throttle body cleaned

• ECU adaptations reset

No fault codes, no loss of power, and the car drives perfectly once stabilized.

Has anyone experienced something similar or has any idea what could cause this behavior?

Thanks!

Edited March 19Mar 19 by MaxGosa88

Morning Maximilian

Welcome to the Forum

Never heard of this before but reading what you have done so far I would carry out a smooth running test at each of the established test points ie, Engine cold Engine Hot and after cooling, also check rail pressures. My thinking is one or more injectors are out of synch or not preforming as they should, Cold symptoms are masked as more fuel is delivered by the DME Hot fuel atomizes faster so it again may be masked.

Hope this Helps

Dave