code p0300 popped up yesterday. it was about -3C out side this morning and when i went to start it up it misfired so badly that it stlled. then i cranked it again and it did the same thing. then i cranked it again then it idled no problem but then when i went into drive it misfired so badly i pulled over and then it stalled . i hooked up my scanner and the only code that popped up was p0300 multiple cylinder missfire. then i went and turned it back on and the idle was fine and now it was ok and ran like a champ.
the misfiring has happened for the last two weeks but i was always at idle so i was going to go get a new IAC and hopefully it would cure my symptoms but now im not to sure. i have put in new plugs 6 months ago, new tbps, and cleaned the throttle body with sensor safe cleaner with the iac tapped to prevent any contaminants entering it.its got new plenum gaskets and fuel injector orings.
also this usually only happens from extended periods of it sitting such as over night or throughout the work day.



now today i go and hook up a fuel pressure gauge and put it into run and it went to 51psi. turned in on the pressure jumped to 59 psi probably because of the increase in demand from the cold temps. let it run for a bit and no misfires today. i then shut it off and it went down to 51psi in the system and stayed there for over ten minutes. now the thing is yesterday was the only day it misfired while driving, it usually only does it at idle, then again it also took longer than usual to crank and turn over.

here is a shot little video today when it had no problems really is this can help at all
any ideas

You said you installed a new throttle position sensor 6 months ago. Was it oem or aftermarket? These trucks seem to not like aftermarket sensors.

aftermarket.

Yeah, I would change it out for an OEM...and any other aftermarket engine sensors you may have installed.

Also, not sure what plugs you put in, but OEM plugs seem to cause the least amount of problems in these engines.

According to the 2005 Dakota Parts List, the spark plugs for the 4.7L models are as follows:

Non-High Output Engine: RC12MCC4 - Champion Copper Plus, part# 439, gap .040
High-Output (HO) Engine: RC7PYCB4 - Champion Platinum Power, part# 3340, gap .040

today it popped a code that said crank shaft position sensor
A circuit. so i am going to replace it and see how it goes.

on first start up, high idle will increase fuel pressure, once it settles down so will the pressure, also have you been going to the same gas station regularly? now that the colder temps are coming around the winter blend gas is here, all the containments they use to keep gas from freezing may be your issue, either switch to a higher octane and see what happens or try a few different gas stations, but I would try 93 for awhile to flush out any crap in the system