SEEMS TO RUN FINE IN IDLE, LOW OIL PRESSURE LIGHT, WANTS TO STALL IN MOTION.

The oil pressure warning light is designed to illuminate any time the oil pressure is too low (below a pre-set engineering-specification). Low oil pressure can be caused by an oil level that is too low, a faulty oil pump or worn out engine bearings. The light could also potentially illuminate if the engine idle speed is excessively low (near stalling condition) due to the slow rate of pump rotation. There is also the possibility that a failure in the oil pressure warning circuit is causing the light to illuminate inappropriately; this could be the result of a failed oil pressure sensor or other wiring issue. Because the other symptom present is an engine stall (shuts off) condition, I'd recommend inspecting for a mechanical issue first. Ensure the oil level is correct, then attempt to turn the engine over by hand using a large ratchet on the center crankshaft pulley bolt; if the engine can be rotated it was not stalled out by a seized condition (which could be caused by a lack of oil pressure). If the engine runs but idles low, I'd suggest raising the RPM to see if the light goes away and prevents the stalling-out. If everything appears OK with a raised idle then the idle control system should be inspected. On the other hand if the light remains on, a mechanical oil pressure gauge should be installed to the oil pressure test port (near the oil filter) to confirm whether or not the oil pump is producing adequate oil pressure. You can read more here: https://www.yourmechanic.com/article/how-do-you-know-if-the-oil-pressure-gauge-is-bad

You need to find out why you have low oil pressure. It is normal that as engine rpm's increase, the oil pressure will rise- the oil pump is moving oil faster. Even though your light goes out, you could still have critically low oil pressure. There should be sufficient pressure at idle to keep the light off. The light will come on when your oil pressure is almost nil- I believe for some it's as low as 8 psi. Normally, oil pressure at idle is specified anywhere from 15 to 40 psi. You would have to check specifications for your Expedition. To verify oil pressure, hook up a mechanical gauge at the oil pressure sending unit on the engine block. Check with a local shop.

The causes run from easy, simple to budget busting ruin. Low oil level, wrong grade oil, real old oil, oil leaks, internal oil leaks, worn oil pump, worn crankshaft bearings. It was pretty common on older very high mileage cars to have a fluttering oil light at stops and idle. It was time for a rebuild, or time to look for another car.

id not drive it or even run it with low oil pressure.. boom $3000 in to rat hole?
or did the engine stall. RPM goes to zero so does oil pressure.
all normal for a stall. did it stall????????
if not check fuses.
if did, diagnose stalling, ask !

If you don't believe that your idle is irregular and lower than normal, you may want to check the oil level. The indicator is for low oil pressure which can happen when the engine is about to stall or if the oil level is low.

did you use correct oil weight could be sending unit. high miles?

you must have a OBS2 scan and get the code for further help.
it can be a number of things.
go to autozone and see if they will scan it for you
as of the oil light when your engine Begin's to stall it will cause it to come on.
post some more info when you get the scan

You mean the light shuts out the truck dosn;t stall right Yes then i would try replaceing the sending unit likely is the cause of the problem

Did you try changing the actual oil pressure gauge?

200 rpm's will diffenetly create a very low oil pressure signal. I can not see how your engine will run at 200 rpm's neither. check the voltage output of your altenator for if its bad this will cause a problem such as yours

change your oxygen sensor thet is whyoillight lights on