Oil pressure problem

put oil in the engine

The oil pressure light coming on at idle is not a big worry, so long as it goes out as soon as revs rise.. First step is to remove the oil pressure sender unit and screw in an oil pressure gauge. a mechanic can do this for you. This will tell you if the sender is faulty (common enough) or the oil pressure is low. A rule of thumb is to have about 10 psi per 1000 RPM in the normal rev range

If it is indeed low, possible causes are
- worn big end or main bearings (the car is old enough)
-faulty or weak over-pressure relief valve in oil pump
-worn or faulty oil pump
-blocked or sludged up oil passages
-blocked or sludged up oil pickup strainer mesh in sump

Some of these can be investigated by putting the car on a hoist and removing the sump
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if you have a 4jx1 3.0 engine then the engine wont run properly because engine oil pressure is what drives the direct injection system.
Check for blocked oil filters 2 pieces if not remove the oil pan and check the oil pickup tube for oil sludge blockage

Yes I would say the oil pressure switch is faulty. The oil pressure gauge uses a different sensor, so if the gauge did not drop but the warning light came on, I would have the warning light switch checked. If the warning light comes on, the fuel pump will stop getting power and you will lose fuel pressure too.

The proper way to determine what's going on in your engine is to install a temporary (or permanent) mechanical gauge. (yours is electro -mechanical) your oil pressure changes with engine rpm but at idle, it should not drop below 15psi (I don't accept less than 20). The gauge and light is set to come on at a pressure that is just a bit higher than the max low pressure so you have a chance to correct the cause without destroying the engine. (though sometimes even that repair can be expensive).
Since the gauge setup or having someone put a gauge on there costs more than a new sending unit for your current arrangement, I'd suggest you replace the sender and if you see identical readings, then you need to have the oil pan removed and the crankshaft bearings and oil pump looked at.
Doing nothing can cost you an engine.

I would replace the oil pressure sending unit first and see if that corrects this.

Make sure the oil level is correct. If the engine bearings are getting worn, the oil pump is worn or it's screen plugged, that can cause low-RPM weak oil pressure. Try running with 'high mileage' oil at your next oil change and always replace the filter. At some point, you may need to consider overhauling or replacing the engine. Good luck!

The oil light indicates that the engine's oil pressure has dropped below the minimum safe pressure. When the light goes out it suggests that pressure has been restored to a sufficient level for engine lubrication but this is nevertheless a bad sign.

I suspect that the oil level in the engine is too low and that the oil itself has greatly deteriorated and has not been changed for some time.

1. Check the oil level again, after the car has been standing for a few minutes, and make sure the engine oil level is at the maximum mark on the dip stick. If not then top it up.

2. Have the oil (and oil filter) changed in the car as soon as possible and ensure it is the correct spec viscosity oil for that engine .

3. Brake test the car to see if the oil light still comes on under braking.
If it recurs you need to have an oil pressure gauge hooked up to the engine (by an auto repair shop) to see what oil pressure is being achieved at various engine revs. If an independent gauge shows no problem with oil pressure then I would assume a faulty oil pressure sensor.
If the pressure gauge identifies a lower than normal oil pressure in the engine's lubrication system then the cause needs to be identified and fixed.

Sean

That sounds like you bought big problems. Oil ights indicate low oil pressure= BIG BUCKS. I would have a qualified repair shop check it out, A shop that specializes in BMW. If you are lucky, maybe the oil sender is just bad. They can also check out the Ck eng light. But the oil light is priority one.

Check your oil level in the engine. Oil pressure will read this way when the oil level is getting low...