I have a 1998 with the 4.6 with 104000 miles.After slowing
to a stop it will hunt for an idle position .It will drop to 300
rpms then shoot up to about a 1000, sometimes it will just
die. Same problem that youre having. Where is the IAC loc-
ated at, and what does it look like. Same question for the
TPS. Thanks

 

I have a similar problem. My 98 F150 4.5L dies intermittently when I come to a full stop with the transmission in drive. It feels like the truck is trying to pull against the brake but the RPM drops and the engine shuts off. Sometimes restarting allows it to idle in drive; other times I have to shift to neutral or park to keep it running. My dealer changed the Idle Control Valve but that didn't make any improvement. A transmission specialist at the dealer said it could be sticking in a higher gear. Any of this sound familiar?
George

 

Had the same problem with my 97 F150, it turned out to be a collapsed pcv hose elbow joint located passenger side behind valve cover up by the firewall.
If I were you I'd find your PCV valve (usually pass. side valve cover) and trace out that vac hose going around back. Cheap Fix too.
Hope this helps.

 

I checked the PCV lines and saw no obvious kink. Should it be obvious?