Could be multiple reasons, sludge, out of tolerance rockers in the head, slight exhaust leak due to a crack or bad gasket. You should probably take it to a trusted mechanis for best diagnosis.
I sat in my car in the driveway with the car idling, waiting for the kids to come out.
The same on a car equipped with manual transmission. On an automatic equipped car it will use less idling.
It depends on how long you are idling, or how fast you are going. If you know you are going to be idling for a long time, it's best just to put your car in park.
Idling is what your car is doing when it is just sitting somewhere running. As soon as you press on the gas it is no longer idling. Your idle speed is the number of RPMs your engine runs at when you are idling.
If a car shakes and loses power when idling it can be the spark plug. If a spark plug is fouling, it can cause power losses.
moving
by the idling air control valve
A car that is stopped with the engine running.
If the car dies while idling, the timing might be off. Other causes can include a clogged fuel filter or a bad spark plug.
There are many reasons why your car might vibrate while it is idling. It could be running too hard for example.
A failing throttle position sensor will cause idling problems when the car is warm. The failing sensor can also cause the car to stall when idling.
There can be many reasons why a car surges while idling. Some of these reasons are the computer could be dying, or the fuel injector are giving the engine too much gas.