erratic oil pressure

1996 cherokee sport 4.0L inline 6 cyl. 130,000 miles

I am original owner and perform all oil changes regulary with 10w-30. The problem that I have noticed lately is the oil pressure being erratic. When I start the engine the oil pressure will be around 40psi or so and it will generally hold that even when it is hot, but when I am driving down the road and I push the clutch in, the pressure will spike up to 80psi (max on guage) and then erratically fall back down to 40 and hold steady as long as I hold the throttle steady. If I push down on the throttle, it may spike up again, but it will usually slowly fall back to 40psi and hold steady. :screwy: Could this be a bad sending unit? I am not sure what to think, since the pressure indication is High and not low, so I am confident that the oil pump is working. Also, there is a small amount of vibration noted on the upper end of 3rd and 4th gears when shifting. Are these 2 symptons connected?

The pressure control valve on your oil pump is stuck wide open.

i have a similar problem. mine runs pretty constantly right above 40psi. all of a sudden, the needle will max out, farther than 80, mine goes all the way to the screw on the right side of the guage. it will stay there momentarily and move a little bit. tell me if something fixes it.

Had the same problem.. rev the engine and the gage would pop pop to 80 .... Changed the pressure sender and it works fine now. Strange thing was that at idle it would set at 40 and as you slowly reved the engine it would spike to 80 and drop back at random. Sender fixed ti.

Ron