Need help figuring out an engine stall issue.

When it happens, I get the lean codes P0171 and P0172.
Seems to only happen when the engine is warm, such as when we drive it around town, then park for an hour or so, then start it and it happens. Straight hot or cold doesn’t happen.
Also seems to happen more often when I’m parked slightly uphill.
This happened with the original engine, its rebuild version, and now with the Jasper engine (Ford dealer installed) so it has to be a sensor, not the engine.
I’ve tightly clamped all of the vacuum hoses, checked for vacuum leaks and have found none by my methods, and replaced all the old stiff hoses I could find.
When it happens, I can “clear” it by running the engine at about 2000 to 2500 rpm for about 20 seconds then it will idle fine. I get a smell of gas out of the tailpipe which tells me its rich. I guess the lean codes are adding the extra fuel?
Any suggestions please as to what else I need to check?

 

Truck details, please? Year and engine at the very least.

Check your codes again. P0171 is a lean code, P0172 is a rich code, both bank 1.

 

2001 f150 supercrew, 4.6L, automatic
i will do that tomorrow

 

codes are P0171 and P0174

 

Seems to me you need to get someone with a smoker to find the vacuum leak.
ChrisFix has a video where he hooked a shop vacuum to the tailpipe, reversed the flow and used soapy water spray on the hoses, vacuum booster, etc to find a vacuum leak.

 

Okay, that's lean both banks. Follow the line from the PCV valve to the back of the intake, check the elbow for cracks and rot.

Could be a dirty MAF sensor. Could be a bad DPFE sensor holding the EGR valve open or a dirty EGR valve. Could be a weak fuel pump, clogged fuel filter, or a bad fuel pressure regulator. Could be dirty injectors.

 

Pull your freeze frame data and report those stored bits of data. They will help guide diagnosis.