[Rabat13]

Hello Everyone!

I'm a first owner of BMW F30 318i 2015 (Engine: B38B15A, Gearbox: GA8HP50 automatic) and from some time I have a problem with RPM increasing when starting on a cold engine and with the car shaking when first changing gear to D or R.

The situation is as follows:
1. I start the car - the car starts properly, then raises the RPM to approximately 1400 (sometimes lowers, then increases again).
2. I wait until it "calms down" to approximately 1000 (it takes 10-15 seconds).
3. Then I put the gear into gear and the revs suddenly drop below the nominal 800 and the car starts to shake, and then the car quickly increases the RPM again to about 1000.

This only happens when the engine is cold, then after driving the car starts normally at 800-900 rpm, there is no tremors - everything is fine. I also have no problems with the gearbox, gears change correctly and ODB2 does not show any errors.

I went to two mechanics - the first one replaced the spark plugs (OEM) and cleaned the throttle (I didn't leave the car for him overnight), and the second one, when he started the car in the morning, heard the sound of the timing chain and recommended immediate replacement (the mileage of the car was 90,000 km).

The suspicion was that a loose timing chain could upset the variable valve timing. I replaced the timing belt (without replacing the vanos) and the oil in the gearbox and engine. The mechanic made modifications to the ISTA - he increased the engine speed under the gearbox and air conditioning loads, and re-adapted the vanos.

Unfortunately, the problem still persists - it only happens when I start the car after a long stop and when the environment is warm. Maybe someone would have an idea what the problem could be? Thank you!

Below is the video before and after replacing the timing belt (in 30sec you can see drop below the nominal 800 and I fell shaking).