Engine Oil Light Flickers

[jonas]

hi, all
2002 taurus ohv 3.0
a problem cropped up after i replaced 10w-40 with 5w-30, the engine oil light starts to flicker at idle or non acceleration, for example, waitting for the light. It only comes up after running some mileage or after autoroute, then stop the car. This never happens during running or accelerate even hit the gas at idle. Besides, when the engine is cold, it doesn't happed even though at idle.
Before changing oil, it never happened, so what's the most possible problem?
thanx

[qwertz9586]

Does it idle funny or perform out of the ordinary? I'm thinking the oil level may just be low.

[jonas]

QUOTE (Qwertz9586 @ Nov 15 2009, 05:02 AM)

Does it idle funny or perform out of the ordinary? I'm thinking the oil level may just be low.[/b]

no, it goes well.
oil level is not low.

[pawpaw]

I've seen oil filters cause this problem, are you using the specified Motorcraft oil filter????

[Popeye]

You are now using a thinner oil. When it's cold the oil is thick so no problem. Once the engine warms up the oil thins slightly so the idling oil pressure is reduced. This does not necessarily mean that you have oil pressure problems. The oil pressure light sending unit may be weak and turn on the warning light too soon. The sending unit is cheap so I would try that first. You might also want to verify the actual oil pressure using a pressure gauge.

The reason the light flashes at a warm idle is because that is when the oil is thinnest and the RPMs are lowest; consequently, the oil pressure is also at its lowest. Once you step on the accelerator the revs pickup and the oil pump works harder to raise the oil pressure.

I hope this answers some of your questions.

Good luck, Popeye

[nbpt100]

QUOTE (jonas @ Nov 15 2009, 03:48 AM)

hi, all
2002 taurus ohv 3.0
a problem cropped up after i replaced 10w-40 with 5w-30, the engine oil light starts to flicker at idle or non acceleration, for example, waitting for the light. It only comes up after running some mileage or after autoroute, then stop the car. This never happens during running or accelerate even hit the gas at idle. Besides, when the engine is cold, it doesn't happed even though at idle.
Before changing oil, it never happened, so what's the most possible problem?
thanx[/b]

10w-40 seems pretty heavy for a gen4 engine. I think 5w-20 is recommended. Curious why you used it?

I would agree with Popeye that the gauge may not be accurate and you should try to confirm what the oil pump is actually putting out for pressure. The pump may be worn out.
Too bad there is no oil pressure gauge on the dash.

[Bull Geek]

sfontain was having a similar issue IIRC...might want to check some of his threads out. He has a 02 Vulcan as well.

[sfontain]

QUOTE (Bull Geek @ Nov 15 2009, 11:23 AM)

sfontain was having a similar issue IIRC...might want to check some of his threads out. He has a 02 Vulcan as well.[/b]

Hah, I was just going to chime in on this.

We have exactly the same model year and engine, and I had the same trouble with 5W-30 synthetic (SuperTech from Wal Mart). I went to 10W-40 conventional and the light disappeared after about 20 minutes of running the engine. (Why it wasn't instant, I can only guess.)

Do check your oil level, but if it's only happening at idle then I'd say that's probably not the issue.

If it happened immediately after changing the oil, also spend the $4 and put on a new oil filter. This will take you like 3 minutes.

You can replace the pressure sending unit if you really want to blow $30 at a dealer (you can get this part for $16 on Amazon; free shipping if you spend at least $25 or have Amazon Prime). But I'm going to go out on a limb here and suggest that it's RARE for these things to go bad.

IMO, your money is better spent on an oil pressure gauge. $18 for SunPro from Advance, or $35 for Auto Meter on Amazon. I have both. The Auto Meter reads lower on the low end of the range. Either way, if your gauge shows 8 psi at idle, that's going to be a hell of a lot worse than if it's showing 13, and you'll have a little better idea how bad your problem is. If the light is only flickering, it stands to reason with me that you have a wear or clog issue slowly developing that is only going to get worse, but how quickly it will progress is purely speculation.

Odds are, you do actually have low pressure at idle. I would switch back to 10W-40 and consider tearing apart your engine to check the oil pump and pickup screen and bearings; if you don't want to do that yourself (and it will be a pain in the ass), it might be time to consider getting rid of this car. A dealer will charge you ~$500 to change the oil pump, and $1000-$2000 to change the rod bearings. Just FYI, my opinion is 10W-40 is perfectly fine for this car despite that it's spec'ed for 5W-20, so long as you don't live in an extremely cold climate. Your fuel mileage may drop a little, though.

In case you or someone else does take apart the engine, please let me know what you discover. I'd like to know if this is more likely bearings or the oil pump/screen.

[jonas]

it's the problem of pressure switch.

[yiranhu]

QUOTE (jonas @ Nov 22 2009, 10:26 PM)

it's the problem of pressure switch.[/b]

Agreed. The flickring light at idle usually indicates a leaking switch. If u wanna be sure, get the oil pressure mentioned by installing a gauge in the same spot that the switch is installed.