RPM reving
 

Hey my Ranger begins to rev when I'm in park and then drops rev when I go to drive. Any ideas what can cause this? ?

It is important to know the year of the vehicle because different years use different methods to control idle speeds.
The list could include,
Charging system problem
Idle speed control
Shift selector (MLPS) manual lever position switch not sending correct signal to engine computer where computer thinks it is in gear when it is in neutral
Possible electrical connection problem in wiring to computer

Ok thanks alot