What is the idling jitter of Sierra engine?

Hello, unstable idling vibration is generally caused by abnormal mixing ratio and poor combustion. If there is nothing abnormal when the vehicle is driving, it is only unstable idle vibration. I suggest you focus on checking whether the throttle is dirty first. If it is dirty, clean the throttle and reset the observation. If there is any abnormality, check whether the spark plug, ignition coil and fuel system are abnormal.