4.0 idle problems

[SBRanger19]

having trouble with my idle, starts up fine but after driving for a couple minutes it wants to die when shifting into park or neurtral. even starting up cold it goes to high rpms which is normal but soon drops to 1000 rpms when still cold. after driving i put in park and the rpms go down to about 150 - 200 rpms and almost dies then climbs back up to 500. the rpms in gear are higher than in park

whats the deal???????

 

[SBRanger19]

ive replaced the IAC and cleaned the mass air flo sensor. ive gotten a suggestion to change spark plugs but if u know how to fix or have had the same problem then explain what to do

 

[Kroeter]

my idle was severely jumping up and down. I replaced the IAC as well and it ook care of it. May want to clean the throttle body as well.