Sensor

Try downloading codes from the OBD port. Auto parts stores might do it for free.

JOHNNY G. JR is right. Reading and recording diagnostic fault codes is the place to start, but sensors do not cause rough idle. Some of them report the results of a rough idle, but they do not cause it. When you have an engine running problem, you need to list which engine you have. The most common cause of rough running is a cylinder misfire, and the most common cause of that is worn spark plugs or a defective ignition coil.