A couple of months ago my car was making this woodpecker or clicking noise under the valve cover everytime my car went to sleep after locking the doors or upon opening the doors after the car had been sitting awhile (see this link for the noise
). The car did not have any check engine lights, but it did run just very slightly rough when starting the car. Luckly I bought a BMW scan tool that can read “soft” error codes. The errors I was getting was 135808 – Valvetronic Servomotor and 135A08 – Valvetronic Servomoter position sensor. I took it to the dearship and they replaced Actuator ($1897). If anyone is interested on what BMW valvetronic does see this link
.