1989 XJ 4.0 auto 4x4 82,000 miles

I just noticed today that my oil pressure gauge is moving up and down while driving, stopping, making turns (like 90 degrees), going up hills.

It seems to go down at turns to about maybe 5psi (gauge isn't numbered) after I straighten back up in about 5-10 seconds it rises back to ca. 36psi.

When stopping it will fall then after accerlation it takes about 5-10 seconds to rise back up.

I've already done some reading on this. I have no idea if it did this when I got it. It could have been doing it since I got it and just now noticed it.
I got it at 78,338 miles and changed the oil. It's now 82,500. So I getting ready to change the oil. I ca t remember if I used 5w-30 or 10w-40 last time but I'll be using 10w this time.

The above is general it doesn't always do it. Is this common or hurting anything? It seems to run and drive ok

 

There is an oil pressure sending unit (sensor) located right above the oil filter.
Check the electrical connection to make sure it's tight. The pressure tube in the motor tends to get gunked up after a while (though you barely have any miles on your Jeep), but you could try unscrewing the oil pressure sensor and sticking a pipe cleaner or something in the tube to try and dislodge any gunk. Some guys use a standard threaded adapter routed to a hose, and the starting the engine to basically "blow" any of the gunk out of the tube (and not into your motor). Kind of messy but effective if that passage is blocked.

If that doesn't work, replace the sensor and see if the condition still exists.

I would usually say throw a manual pressure gauge on the motor for testing, but it you would need to run it into the cab if the condition only exists while you are in motion.

 

Ok. When I crank it it idle. It idles at 36psi. I also read that old broke down oil can cause this. It's been 4,000 miles and if I mistakenly used the 5w then it could just be getting old.
So I'll check that connection and then change the oil as it needs it anyway.