Ok here is what I have going on. I have a 2000 V6 with 96000. This has happened twice in the last week, at least that I have noticed. I start the car up and I get oil pressure right away according to the gauge. Then after a half minute the gauge drops all the way down to low for about 5 seconds then back up to normal. It may do this 3 or 4 times then it returns to normal and no problem from then on. I also don't notice any tapping from the engine when the pressure is on the low side. Also the gauge does not go all the way down past low like when you shut the car off, so I don't think its in the wireing. Any clues on this. I am thinking oil pressure sending unit or could this be a check valve problem. Also any info would be appreciated on where is the sending unit located on this car. I have the Haynes manual and can't find it in there. Yes the car has the correct amount of oil in the engine.

 

My mom 00 mountaineer does that except when she starts it up it will be all the way to the bottom and it beeps and says check guage. Then after about 5 mins it jumps up, then down, then back up to normal for the rest of the time you drive... don't know what it is though.....

 

its the oil pressure sending unit. mine did it a while back and its common for it to do exactly what your describing when it goes out. go to autozone or somewhere like that and get one. they are cheap, like under $5. to replace it pop the hood and look behind the power steering pulley and you will see where it is screwed in. unplug the connector and unscrew it. screw the new one in plug in the connector and your good. easy fix.