So ive had this problem for a few days now. First i replaced the battery and alternator and she ran fine for most the day and then shut off by itself, it would crank on then it would sit under 1k rpms and then drop and die. Ive replaced alternator, battery, fuel filter and fuel pump and its still happening. Ill try and link a video to show how it starts. Any ideas would really be appreciated.
Forgot to mention, after waiting a while she would start up just fine and run clean.

 

what year? how many miles? no CEL?

 

Sever throttle cable stretch?
Extremely filthy throttle plate and throat?
A vacuum leak?
A bad IAC (Idle Air Control) valve?

Year, miles etc. do help.

 

Its a 2004 ford ranger v6 4.0, and zero lights on the dash
and just under 160K miles

 

Also i shoulda mentioned that it really only seems to do it in park

 

The PCV system is a source of vacuum leaks. It has a large, "L" shaped run of hard plastic pipe going from the PCV valve, across to the other side of the engine and forward to the intake.
This plastic piping can crack with age.