2000 F-150 5.4L V8
Last winter my truck started bogging down after starting and the RPM's would bounce up and down. The problem seemed to go away after driving for a minute. Now summer has hit and the problem has started all over again. I finally realized that with the AC off it was idling fine, but I have no idea what the real problem is. It is only happening in the cold or hot, and just the first start after the truck hasn't been driven for a day. Thanks

 

Might want to check the IAC valve. Last winter mine would start right away then rpm's would drop almost to a stall for no more than about 20 seconds before recovering. Replaced the IAC and no problem. It is basically an air bypass valve that controls air bypass into the TB thus controlling rpm. Gets dirty and stops working. Some say you can clean it do a search for more about that. I replaced mine then later tried to clean the old one with little success.

 

mine does the same thing, but it almost stals out when the ac is off, when the ac is on everything is ok,don't know what is wrong, don't know how to fix it. mine does everyso often drop below 500 rpms when the ac is on, but it mostly happens when the ac is off and it usualy dosen't do it until the car has warmed up. does this sound like the same problem?