recently, my 2001 4.0 explorer, when starting ,, after over night,or after all day parked at work, there is no oil pressure,for a while, and engine runs rough, maybe a minute before oil pressure starts,
i just had an oil change, could they have put in a bad oil filter? or the wrong weight oil?

 

I know this is kind of late, but I just found this site. We just purchased a '00 with 4.6 efi. and found the same problem. I changed the oil but to no avail. The engine seems to run ok, but the pressure guage doesn,t move for approximately 3.5 - 4 minutes. David

 

I also have this problem, managed to find a possible cause. From the most unlikely source of ebay.
When the chain tensioner wears, the particles work their way to the sump (pan) they then get picked up by the strainer which clogs, this causes a slow pressure build up. As of yet i haven't done mine as i've heard i need to remove the engine to strip the sump. Only being a humble man i don't have the tools or time to do this.
So if any one can shed some light on this matter please let me know.
Cheers the English bloke in Germany

 

run an engine flush through it and on the next oil change all should be well again

 

Tried the engine flush, didn't work.
Will leave it a while then try it again.

 

hi, i got the same problem as well, i just wrote one post, that talks about

https://www.fordforum.com/m_16895/tm.htm

So i hope the pressure sender is the answer to this problem. i have no idea what is a pressure sender. but well i will have to find out