1998 explorer will not idle when cold, any ideas?

[Blackout51]

I have a 98 sport 4.0 sohc, I was getting the codes saying that both bank one and two were reading lean and the high idle code, I had my fuel filter swapped and then everything ran perfect, well it still didn't idle cold but one warm there was no codes and idle was correct, but today out was colder than it has been and I went to stay it and it idles for about three seconds acting like I've disconnected three of six spark plugs our something and then it dies, but once warm it was doing good then all three codes showed back up, I had driven it for days and the lean codes were gone, any ideas? I've replaced the upper intake manifold gasket but not the lower and I've done a carb cleaner leak test and got no results

 

[koda2000]

it sounds like intake manifold gasket/o-ring air leaks (upper and/or lower). why would you go through the trouble of having changed the uppers w/out doing the lowers? if you want to fix the problem you're going to need to do both. the fact that it runs good once warm reinforces my opinion.

 

[Blackout51]

it sounds like intake manifold gasket/o-ring air leaks (upper and/or lower). why would you go through the trouble of having changed the uppers w/out doing the lowers? if you want to fix the problem you're going to need to do both. the fact that it runs good once warm reinforces my opinion.

Well I changed the thermostat and only took off the upper manifold so I figured change them while i had it off, but how does that explain it having the lean codes then not for days where it did get started from cold start and then again today it has them again, I'm sure they do need to be changed I'm just confused how a lean code can go away and come back, it seems like it'd be a pretty good coincidence a lean code from fuel filter gets fixed and three days later a lean code from manifold gasket