Oil pressure gauge fluctuates

[timd]

After driving at highway speeds, if I come to a stop (750 RPM), the oil pressure gauge flutters wildly until I raise the RPM's above 1000. This is on a 2002 with a 3.0L engine, 117K miles only. Oil level is at full mark. Using the recommended 5W20 oil.

[65comet]

Several possibilities.
Most likely for the age the oil pump is going out.
A bad gasket might have let anti-freeze get into the oil. Just a small amount can mess up the ability to keep up pressure.
The oil pickup tube or the pickup screen is clogged.
The pressure might be ok and the sender is actually going bad.

The best thing to do is find out what the real oil pressure is by removing the electric sending unit sensor and putting in a true gauge. A cheap one can be gotten at a store like harbor freight and there are tons of videos on how to check the pressure on youtube.

[timd]

65comet: Have been searching for the oil pressure sending unit but have come up empty. The one diagram I found online shows it on top, on the left side of the engine (facing it from the front) midway back but I didn't find it.

[65comet]

Here is a video for a Taurus with the same engine that shows the location.
https://www.youtube.com/watch?v=owWbK_cltv0

[timd]

Thanks for the video. Checked my engine but didn't find the oil pressure sending unit.I have only 117K miles on the truck so I'm hoping it's not the oil pump. Here are some pix that may help identify which 3.0L engine I have.

[bellaCuba]

I can tell you now, oil pumps rarely fail.
I can almost guarantee the oil pump is not the issue. You more than likely have a sticking oil sender, it's going bad, or the wires rubbing or that "frequency" at that specific RPM vibrates.

I'll see if I can post a diagram of the sending unit location.
I couldnt find a "wide angle" shit of the location, but I can tell you how to find it with the aid of a closeup view on the diagram. Sitting in the vehicle, the oil sender is on the right rear (by the firewall) side of the engine. Almost by the bellhop sing of the trans but it's on the engine block at the end of the cylinder head. https://www.dropbox.com/s/424pxckw7p...54.09.png?dl=0