Rough Idle

When ever i have it in park, Nuetral or even drive and i let it just sit there, it will start to shake a little hard.. any reasons?

There could be a lot of reasons for a rough idle. When's the last time the vehicle had a tune up? Have you checked the spark plugs, plug wires, replaced the fuel filter, and checked for vacuum leaks?

You may want to start by adding a bottle of fuel injector cleaner to the fuel tank. Drive it a hundred miles or so and see if it has any effect.

Also, at idle, the EGR valve should be closed. If there is some carbon in the EGR valve preventing it from closing completely, that could certainly cause a rough idle.

Which engine does your Explorer have?

-Rod