Oil pressure

So i just got my 89'xj this past weekend. It seems like there is somthing wrong with the oil pressure. Today when i was stopped it was very low. 10psi mabey, i was parked and tapped the gas to try and get the idle up because it seemed like it was idleing low too. Also, at speed when i let off the gas especially down hill the gauge pegs its self all the way up. Then when i get back on the gas it goes to around 40-50.
Do you guys know what this could be?

Also there is oil in the dirty airfilter...could that have anything to do with it?

Any help would be greatly appreciated
:helpme::helpme::helpme:
http://www.naxja.org/forum/editpost.php?do=editpost&p=244579847

Normal oil pressure is-- Hot,10w-30,idle(750 rpm) 10-13 psi,above idle(1600 rpm) 40-75 psi.
Oil in the air filter is normal for that era engine,clean the ccv tubes and grommet to let it breath better

Wayne

You may have a bad oil pressure sending unit. A very common failure on the Jeep 4.0 You could just replace it (I'd recommend buying from Jeep for best reliability/accuracy with your factory gauge) or if you're ambitious, temporarily install a mechanical oil pressure gauge where the sending unit resides to get an absolute verification of your oil pressure.

As for oil in the filter/filter box, as already mentioned, it's common for your vintage. Search for BLOWBY and you'll get pages of light reading and good recommendations. Blowby is not a death sentence for your engine. Many XJ owners have very good luck managing this condition.

Agree with the other posters, for sure rent a mechanical gauge and test the pressure, IP gauges are notoriously poor.

Make sure the ccv system is functioning properly, that the fresh air intake hose to the front of the valve cover isn't collapsing, that the orifice in the rear grommet is open as well as the intake manifold port, and that the rear vacuum line is clear.

Just for Grins and Giggles, what oil viscosity/brand; what oil filter?