2000 Ford F150 Too lean bank one, Cylinder one missfire

first well go over the hard idle. sounds to me that your coolant temp sensor may be bad, also the IAC may need a cleaning, check the housing on the IAC and the IAC itself if you notice any maring fix it, also the pintle on the IAC should be moving freely. Also clean the throttle body

for the missfire you may have a bad fuel injector, is the cylinder getting bright blue spark? if so check hte compression on it and clean the injector.

hope this helps.

It sounds like you have a bad lower intake gasket. This would explain the lean code on bank 1 (cylinders #1, 2, 3, 4 on passenger side). This would also explain the miss on cyl 1. The other option is a sticking intake valve, but I haven't seen too many of those on these engines. It also explains why the problem exists when it is cold. Once the metal heats up, it expands and the vaccum leak is lessened.