05 Jetta engine overhaul. Unstable idle speed, waste of oil and slight jitter. Why?

It should be a sensor problem. I have never driven a Jetta. I don't know whether it's an electronic throttle or a mechanical throttle. If it is a mechanical throttle, check the idle motor and intake pressure sensor. If it is an electronic throttle, this situation is generally caused by the electronic throttle. It may be caused by the mismatch between the electronic throttle and the EFI computer due to the failure of electrostatic elimination when repairing the electronic throttle. It is recommended to go to the repair shop to check which sensor of the monitoring computer has problems. This situation is not a big problem.