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Old 04-13-2006, 01:22 AM
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Default O/T - Car loses oil pressure at low RPM\'s.....

I've noticed it only a few times since buying the car about 3 months ago. Maybe two or three times the following has happened....

Driving for a little bit and stop at a light or as in today was in a drive-thru lane at McDonalds and the oil pressure light comes on. I increase RPM's slightly and the light goes off. However today in the McDonalds line the engine would die if I didn't do some funky two footed driving keeping the RPM's up a little. Once I pulled out of the drive-thru lane though no issues. Checked the oil and it's full and where it should be. Today was the first time it's ever died on me.

So what am I looking at here? Just a low idle RPM issue or more? Other strange ideas that popped into my head was wrong viscocity oil, bad pressure sensor, and blocked oil galley. Give me your wisdom please. I've got a Haynes manual already if need be.
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Old 04-13-2006, 01:32 AM
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Default Re: O/T - Car loses oil pressure at low RPM\'s.....

was the motor making noises? knocking etc?

easy way to check the light is to hook up a mechanical oil gauge and see what you're actually getting, the rule of thumb i was always told was about 10 psi per 1000 rpm is good.
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Old 04-13-2006, 07:53 AM
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Default Re: O/T - Car loses oil pressure at low RPM\'s.....

I would agree with Jeepnut nh. First thing you should do is get a good mechanical pressure guage, and see what you really have. Pressure sending units should not be trusted. If your sender is electric (Most cars are) then the light you see is triggered by an electric sig. So, even if your car has good oil pressure... If your sending unit thinks it is "not good" the light will come on.

Another common car feature is a fule pump shut off that is tied into oil pressure. Meaning that if the oil pressure drops below a pre set # for some period of time, the computer will turn off the fuel pump. This is a safey feature that a lot of cars have. So when you hook up your mech. guage... you may run into a no start situation. Check your manual to see if the motor you are dealing with has more than one spot to check the oil pressure.

Also do a quick visual inspection of your sender... if you have wires that are loose, or cut it may be an easy fix.

Good luck, and let us know what you find out.
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Old 04-13-2006, 08:07 AM
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Default Re: O/T - Car loses oil pressure at low RPM\'s.....

It might help those of us without ESP to know what "car" & engine you actually have...
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Old 04-13-2006, 08:20 AM
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Default Re: O/T - Car loses oil pressure at low RPM\'s.....

Also how many miles on the car? Assuming it's not a bad sending unit, it seems that at idle your pressure is low, could be just that the engine is worn, and if the light comes on at 10 PSI or something, that the pressure is actually low.

I'd throw in a can of STP oil treatment, Barhdall's -- whatever thickening agent you see at your local Auto Parts store. Try to thicken the oil a bit, it should increase your low rpm oil pressure. Do you know what oil is in there? 5W-30? 10W-30? Perhaps a 10W-40 or a 20W-50 would improve it. As the warmer weather of summer approaches, you could switch to a thicker oil.

Good luck
Pete
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Old 04-13-2006, 09:27 AM
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Default Re: O/T - Car loses oil pressure at low RPM\'s.....

Some cars are known to be prone to oil pressure problems due to faulty oil pump relief valves. Whatcha got????
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Old 04-13-2006, 10:29 AM
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Default Re: O/T - Car loses oil pressure at low RPM\'s.....

The first Wrangler (95 2.5L) I had did that... turned out it was a bad oil pressure switch. It was cracked and leaking (small amount) oil and (I believe) the fuel pump circuit is tied into it so low pressure = no fuel.

After replacing the switch, no leak and no more pressure/stalling problems.
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Old 04-13-2006, 11:53 AM
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Default Re: O/T - Car loses oil pressure at low RPM\'s.....

Other contributing factors?

Do you have an engine temp gauge? What did it read?
Itís been unseasonably warm here, you ainít that far away.
Hot engine = lower oil pressure.

What weight oil?
How long since the last oil change?
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Old 04-13-2006, 12:33 PM
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Default Re: O/T - Car loses oil pressure at low RPM\'s.....

For most cars the 10psi per 1000rpm rule does not work out. There is a problem, and it could be the oil pump, the sender, or even RPM problems. But, what ever the cause it has to be looked into and solved.

However, the dying problem would really concern me. The the other problems could be a result the dying problem creeping up on the owner.
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Old 04-13-2006, 01:11 PM
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Default Re: O/T - Car loses oil pressure at low RPM\'s.....

Sorry, I completely spaced out when I was writing and forgot to mention the kind of car. It's a 95 Plymouth Acclaim with about 86k miles on the clock. It's got the 3.0 V6...made by Mitsubishi I believe.

No strange noises ever, runs like a charm almost always. I don't know what weight oil is in it, the dealership I bought it used from did an oil change on it when I purchased it. I've put at most 1500 miles on it since then. The temp gauge has been normal, no issues showing on any other guages other than the oil pressure light coming on. And when the light comes on, in bring the RPM's up just a little and it goes off.
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