This morning on the way to work and whenever I let go the gas and the Low Oil Pressure warning comes on.
The weather is 34 degree this morning...
Oil is full and I just changed the oil couple of weeks ago with Mobil1 W5-30.
Any idea ?? Thanks.

 

How far is your drive? Once the engine warmed up did the light stay off?

 

From home to work is 7 miles, but it came on after 5 miles I drove.

 

I'd personally stop driving the car until you figure it out. How many miles on the car?

I think these cars have oil control valve problems around 125-150k concerning something with the vvti system. Someone else can chime in in that if they've replaced these before.

 

I took the car during lunch time to the shop.
The car started OK but Low oil pressure came on and stay on after 500 ft driving.
It drove OK to the shop (about 5 miles from work). Left the car there so my mechanic can check it out, he thinks it the oil pressure switch and that is why car still running otherwise the engine will lock up right away.
Makes sense??

BTW, it is 2001 LS430 with 155000 miles.

 

I would be worried because you said it changes with throttle and rpms which would seem mechanical rather than a dead switch but I could be wrong. Keep us posted what the results are.

 

in my Olds V8, an oil pressure light that came on at low RPM indicated worn crankshaft bearings. Replacing my oil pump helped but only by a little, it still came on. If you can keep that light off by manipulating the throttle then you can drive it but that gets to be a pain I would think. Unless the engine has been abused by infrequent oil changes, then the comment about a vvti issue sounds plausible to me.

 

In almost every motor lower rpm always produces lower oil pressure because oil pump is running slower. Hopefully it is something simple like a sensor is clogged, or weak oil pump. Worse case it is worn out engine but that would be rare on the LS430 engine at only 155k miles if you have maintained the car by the book. I'd also change oil and filter immediately - rarely an oil filter can be defective or get clogged.

 

Yeah, I would start with the oil filter. Since you just changed the oil.

 

Well! Changed the oil filter and top up but didn't fix it.
The mechanic suggests the oil sensor next....

 

Sounds like the next logical step. Let us know.

 

Oh, that car was not on your list. A sensor switch is the next thing to look for because it is easy to replace. If what you described (light on when you let off the gas) is the case, you might have a bunch of gunk in your engine causing the oil to stay up out of the pan and not drain back to the pickup in time to get the now slower spinning pump to keep the pressure up. Hopefully it is simple like the sensor.

 

The warning light came on when I let off the gas at first but now it stayed on no matter what.
I was thinking about using the ATF fluid to get the gunk loose...

BTW, I sold my SC430 last week and forgot how to change my signature Lol.
Found this 2001 LS430 for $7500 not sure if it is good deal or not...

 

UPDATE !!!!
It was the oil pressure switch.....

 

Glad you found the problem. Not a common one.