4.0 V6 idling high and funny...

His description still doesn't match that behavior very well. Even the manual doesn't hold an 1800 rpm idle after its warmed up.

 

I have a manual, and mine doesn't do that. The behavior he is describing sounds like mine after the battery has been disconnected for a period of time. I know Iroh mentioned this earlier, but I'm wondering if the ECU is somehow dumping it's memory. I recently did a TB clean with the battery disconnected and it took 2 or 3 days for the truck to return to a normal idle pattern. For some strange reason, the AC quite working too and I think it was 4 days later it resumed to normal. That's how it is with computer controls. Hopefully the dealer will sort it out, but probably they will just start replacing shit till it clears up.

 

Turn blower motor off and see if idle changes. My 09 idle goes up and down when blower motor is on. Even on low speed.

 

Idle rpms are adjusted by reading from ect sensor. Your truck seems to think its colder then it is. This is usually due to bad connection. Dealer should be able to sort it out