I have 02 f150 4.6,4x4. This truck runs great when it above 20 degrees,but it is 0 out now and when i started my truck today it idles at 2500 rpms and wont shift when driveing,i can shift it from 1st to 2nd by hand but it won't shift to 3rd or od?? it only does this when its super cold need some help!!!!!

 

In very cold temps, the cold idle can go quite high but should come down in a few minutes as the engine begins to warm.
There is also a timer in the software to force it down after a certain length of time by closing the IAC.
I would clean the IAC and the Throttle body to be sure there is no gum buildup that gets rather 'stiff' in cold temps.
If the Idle returns to normal after the engine bay gets warm, it's a good bet the above mentioned is the problem.
In very cold temps. the trans fluid get a bit thicker and may allow delayed shifts.
The trans has a temp sensor on it's valve control plate that feeds a signal to the computer. This signal changes the shift times and points.
Especially, it won't allow overdrive to engage until the fluid temp approches about 90° +/-.
As you drive from a cold start, the radiator keeps the fluid cool and heats it at the engine temp rate, so it will be some miles until all temps are up to normal.
If there is a problem shifting otherwise, the PCM has control of the shift valves. The valves may be sluggish in cold temps from varnish build up.

 

Do you have any ext heaters i.e. block heater or anything? A tranny pan heater would be a helpful thing, being in Alaska I have one on mine and I dont have any issues and it gets colder than a witches you know what.

 

ok whats a IAC ??? And i have no ext heaters,I think its a sensor of some kind that is froze and not preforming right. But I really don't know,going to put it in the garage today try to thaw it out ????

 

The IAC is on the back of the throttle body, you will need to remove the plastic throttle body cover to see it.



2 8mm bolts hold it on. I cleaned mine 2 times on my 2001 prior to replacing it.

 

It's been in the mid twenties around here and I hadn't driven the truck for a week.

Yesterday, it fired up but wouldn't idle, on multiple attempts.
I took a heavy screwdriver (about 24" long) and poked the IAC a few times.
Truck started and idled fine.

My IAC is fouled and the cold weather really made it stick.
I don't want to clean it right now.
Tapping it is a quick temp fix to get you going, if that indeed is the problem.
(and I'm keeping the screwdriver behind the seat)

 

ok thanks guys !!! Think i got it fixed took the air intake off sprayed some WD40 in the throtle body and she is running fine!!! right now any way,hope it stays that way!!!!

 

Okay. Just don't make a habit of that. Address the root cause as soon as you can if the IAC / TB, etc need R&R.

External heating wouldn't be a bad idea either. Ilike the tranny pan heater

Good luck.