2004 Chevy S10 4x4 stalling at idle. Drove 3 hours last night, no prob, but this morning this. RPMs 200-800, oil pressure gauge flutters, lights dim with the idle, then stalls. Starts right back up.

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

1. As a basic measure I would make sure the correct grade and spec oil is going in the engine. You can no longer trust that a local mechanic or even a dealer service center will necessarily use the required product as stipulated by the manufacturer. It is always better to buy and supply your own so you know the correct product is being used.

2. I would not assume there is a problem with the oil pressure warning light even though there could be.
The first thing the mechanic should have done when you reported the oil pressure issue is to hook up an independent mechanical oil pressure gauge and check oil pressure when the engine is hot at different RPMs. Any oil pressure issue will usually show up at idle when the engine has been warmed up properly and the engine oil is hot (unless you have some kind of intermittent oil pressure relief valve that is sticking). Just replacing parts without actually knowing what the oil pressures are at different RPMs is being sloppy and negligent.
This is what you need to do now. Contact a business that can hook up their own pressure gauge to your engine and have them check the oil pressure readings at various RPMs when the engine is fully warm. If there is a low oil pressure issue it will show up on the oil pressure gauge. As you have a new oil pump there should be no issue now with oil volume or a sticking oil pressure relief valve which on your engine should be part of the oil pump assembly.

3. Worn engines will not be able to sustain required oil pressures. Oil pressure is not produced by the oil pump. The oil pump produces oil flow but the resistance to flow is what produces the oil pressure and that resistance is created by fine clearances between operating engine parts especially on the crankshaft and components connected to it. Once the engine wears the clearances increase and the oil flows past the parts much more easily and produces/builds much less pressure.
How well your engine with over 90000 miles has been maintained depends on how often all the owners changed the engine oil and filter , whether they kept the engine oil level up to full (most owners rarely ever check oil levels between services) and whether they always used the correct product. Manufacturer oil change intervals shown in service schedules can be 10000, 12000 miles or more which is much too infrequent for the type of use 95% of private vehicles experience which typically are on the severe to very severe use end of the spectrum. Engine oil typically needs to be changed at least at half the mileage shown in service books (at least twice as frequently) and thus at least every 5000 miles if you want your engine to last.

they probably didn't set the valve lash correctly one of your cylinders isn't firing correctly get a cylinder compression tester and test each cylinder

Have the engine checked for vacuum leaks, that will cause a high idle speed. As a 35 year veteran of auto repair I can tell you that engine flushs are a 100% waste of your hard earned money.

It may be the oil pump. If the gauge is going up when the rpms increase it's probably not the gauge or pressure switch. If the computer senses the oil pressure is low it will shut the vehicle off to try to save it's self from catastrophic failure. Also it may start cranking longer before starting. Thats it building oil pressure before the computer will let it start. Make sure oil is full, clean & thick.

Low power lean conditions cracked air intake tube GM Testing by a qualified repair person with proper diagnostic tools is the way to a proper fix , not someone guessing !

Hello! As long as the oil pressure does not drop below 10-15 lbs at idle and iccreases with rpm/s I would not worry...Change to a higher range viscosity oil; 10W30 in the summer and 10W40 in the winter and you should not have a problem...Guru...saailer

I’m happy to help further over the phone at https://www.6ya.com/expert/david_6df67de3b14de867

Now you can do the Fuel Pump

They seize up mechanically and fail
Electrically

Did you drive with a fuel pressure gauge,
taped to the windshield

Got a good fuel filter

Looking won't help you

Always do some type of testing,
before replacing anything

98 chev pickup s10 put gas in the gas tank drove it about 2days and the check engen light came on had it check mech said it was the gas cap replace the gas cap the light back on now what help

sounds like a integrated safety shut down in your computer check your temp and oil pressure gauges when the car is running if they are norm check the sending units to see if they are working properly