i have a 2000 ford ranger tremor 3.0L V6 Flex and there some days it idles normal but some other days when i put in neutral it start idling high from 3 to 4000 rpm and then go back down to normal idle in 10 sec. what can i do about that?

 

Probably your IAC valve. Get some fuel injection cleaner(car cleaner for fuel injection) asd spray the crap out of it. While you are there spray the throttle body as well.

 

i bought a new IAC valve and its still doing the same

 

TPS may be sticking.

 

Check to see if the throttle cable is sticking, and check the return spring on the throttle body.

 

mine was doing the same thing until yesterday
check for vacuum leaks
or cracked vacuum lines
thats what mine was