2003 2wd f150 4.6 Triton
Idles high at first start up around 1500 to 2000 rpm for a couple minutes then smooths out, but while driving the rpm will hang up where it was for a couple seconds like cruise control is on, and if I slow down the idle fights me. I assumed it was the temo sensor but replaced with no change. Not throwing any codes after I changed the temp sensor.
My next step is to look for a vacume leak but with how its acting i dont think that's it, it is not constant at all it picks anc chooses when yo stay high in the rpm while driving, and it died in me once when I stopped fast and the idle stayed at about 1300 then died.
Any help would be greatly appreciated thank you.

 

2 possibilities:

1. Sticky IAC.

2. Sticky throttle linkage.

I had the same thing happen to my V6 - the doghouse on top of the engine was loose and the throttle linkage was hanging up on it.

 

Iac is new, and linkage is not sticking.
If I can keep it under 2000 rpm the rpm doesn't hang up

 

I would check to see if you have any pending codes. Confirmed codes will get CEL. So you might have codes, but the truck isn't sure yet to make them confirmed to illuminate the SES/CEL (service engine soon/check engine light).