My 03 4.6 exhibits the following behavior. Cold start is fine and it runs fine and warms up such that the coolant temp rises to normal then shut it off for a while such as a trip to the store. Restart from partially warm (not dead cold) is fine. After start, as the motor settles down to idle after a few seconds, the idle drops and the motor stumbles and almost dies. No codes or service light. Gas it and it runs fine. No issues while warm

 

have you tried cleaning the IACV? it's pretty easy to remove and spray with carb or intake cleaner.

 

not yet. i'm suspicious of the temp sensor too

 

I don't understand why you would suspect the temp sensor for the symptoms you are describing. I agree that you should remove and clean the idle air control valve.

 

Likely IACV or MAF.

 

definitely check the MAF after the IACV. i had similar issues on my '04 a month or three back and it was the MAF. slipped my mind when i posted earlier.

 

Also check the nipple coming off the intake tube which runs to the IAC it'll cause it to idle and act funny if it's torn/leaking. IAC for sure could using a cleaning. You want the valve inside to freely rotate.

 

I've never cleaned the IACV in my truck. It sounds like an easy, preventive maintenance thing to do.

 

it seems to think its warmer than it really is causing a too lean condition. However I don't know if it's too lean. Too rich wouldn't stumble

 

what codes are you getting?