2001 E150 4.2L 6 cyl 220K miles

Just bought it.....

Drove it an hour home.... took forever to get it to stay running (20 min)..... then it idled extremely low run other than that ran really good....

I bought and installed IAC and ran some Seafoam thru the gas with no change.....

I bought some plugs but haven't installed yet....

Really want this van to run good it drives so good...

 

It does have some miles on it.
Until you check everything and look it over carefully , it could be something simple like a vacuum leak somewhere. When replacing the plugs you might come across something that isn't right and you might get lucky. Since you didn't mention anything like a check engine lite on , why not have a place like Autozone check it for any stored codes. Always a good place to start.

 

did a general look over not Tol indepth.... autozone checked no codes

 

There is a difference between history(stored) codes and present codes. Not all codes will illuminate the check engine light.
In older vehicles you could erase codes by just disconnecting the battery. In newer vehicles that can no longer be done. The fault must be corrected and the monitor run and if the monitor passes it will erase the code. If not or the monitor has not run yet for whatever reason the code will remain.
The Powertrain Control Module (PCM) receives info from various sensors and controls idle speed. Does the idle speed run at a different speed when cold as compared to a warmed up engine. Engine temp info has a bearing on idle speed as well as if the system thinks addl charging is necessary it will increase idle speed to increase alt output.
Usually a scan tool that can produce current data may reveal an unusual reading that could help point to the problem.