1997 f150 5.4L ~110k miles
No real mods yet except cold air kit, upgraded plugs/wires (over 10k on all 3 things)

In the last 2k miles the truck has been acting a little weird. The idle seems to set itself about 300-400 rpm higher than normal. The only thing I can tell that is different when it happens is that after start up I start driving pretty quick afterwards, say it's in gear within 5-10seconds but not always. Once this happens it never goes away until I shut off the engine and restart it.

No check engine, pulls hard like normal.. Everything seems normal except that idle, in gear or out of gear, stays high.

I am not really concerned but thought if anyone had any ideas as to why it happens..

I am trying to make sure to let it go through it's quick idle sequence and not put it in gear before it settles on it's own but sometimes ya just gotta get going...

 

search cleaning tb and iac

 

EGR???? probly a leak or bad EGR had it happen to a chevy high idle for 15min- 20min then run like normal worse in cold weather cost $90 for my chevy fixed it though

 

If I were to take a swag at it, I'd guess you have a vacuum leak beginning to manifest, probably somewhere in the PCV tube assembly going from the passenger's side valve cover to the rear of the intake manifold.

 

thats a really good possiblity

 

Thanks for the ideas guys, I'll start checking those things.