**PLEASE HELP**rough idling when cold

[n.shift]

my 2001 expedition 5.4 L eddie bauer edition has developed a rough idle on first start of the day. I'm assuming because that's when the engine is coldest. when starts, it revs up to over 1k rpm's then idles to around 4-500. that's when the entire expedition begins to shake. if I try to drive it under this condition, it literally has no power no matter how much gas I give it.. all this last a total of 30 seconds to 1 minute, then it runs like new the rest of the day. exp. has 95k miles. bought it used couple months ago from private seller so have ni idea about what kind of general maintenance that has already been done. Any ideas? no check engine lights are on, so I am assuming no codes if checked with obdII scanner.. thanks in advance

 

[Bedrck47]

when were the plugs coils and boots last changed, Fuel filter changed. You may also want to check the fuel pressure.
I would pull the Idle Air Control (IAC) Valve and clean it. Also you may want to pull the throttle body and clean it although the exhaust port in the 5.4 TB doesn't normally clog as bad as the ports in the 4.6 TB

Put a code reader on and make sure there are no codes.
Not really a good idea to assume anything. best to check and make sure

 

[n.shift]

fuel filter was changed 2 days ago. fuel pressure holds steady at 30-40 psi while running and drops off a little when shut off. if it sits all night, I suppose the pressure may bleed all the way off. if I left fuel pressure hose on, should it hold pressure at around 30 psi all night? I haven't left it on that long but I guess its a thought. at 95k miles, id bet plugs have never been changed. I have them just haven't swapped them out yet. besides, would bad plugs only cause it to idle/run rough and shake when it idles way down for less then a minute when first started after sitting all night? runs like new the rest of the day. I will inspect all vacuum lines and clean MAF sensor, throttle body and IAC tomorrow. Again, no check engine light on so I'm assuming reading for codes isn't gonna show anything. right?

 

[Bedrck47]

I would go ahead and check vacuum lines and clean MAF sensor, throttle body and IAC as you stated. Change the plugs If they are the originals the are due to be changed. And again as I said never assume anything also best to check only takes a few minutes to check for any codes.

Does the check engine light come on when you first turn the key to the on position without starting. This is a check to see if your instrument lights are working. It should come on and then go off after starting.

 

[n.shift]

yes, check engine light comes on when key is turned on. goes off after few seconds. Ill take it to advanced auto to have them scan it. My exp. turns my code reader on but when I go to run the test, it restarts my obdII tester. maybe it not compatible with my exp. I have seen a lot of threads about the pcv vacuum elbow under the IAC having a hole in it. if this is the case, would it cause it to only run rough/idle up and down/shake for minute or less then run good? or would it cause it to idle crappy all of the time?

 

[Bedrck47]

possible. Get a can of carb cleaner and spray around the vacuum lines if you have a leak you will get an increase in RPM's
Use Throttle body cleaner on the throttle body