Irregular oil pressure

Yesterday I was at the end of a 2.5 hour drive and saw a small puff of smoke behind the xj. Got it home and noticed that it was idling a bit rough. Opened up the hood and saw a small amount of smoke comming up from the oil filter area. After the engine was off for an hour or so there were about 3 or 4 drops of oil on the ground. I've ben watching it all day today, just driving around town. Still idling rough, and the oil pressure is doing strange things. Sometimes it stays constant around 40 on the guage. Other times it changes with the rpms of the engine. No leakage today. Oil is full. No over heating, and no knocking or anything in the engine. Just the rough idle. It's a 96 xj, 4.0, 2wd, 4 door. Any ideas?

Thanks!!!

Sounds like you've got a small oil leak either from the oil filter adapter o-rings or from the oil pressure sending unit. The former isn't a big deal but the latter might be if you don't replace the sending unit soon; they can blow apart completely once they start leaking and dump a lot of oil in a very short time.
Check the plug leads. It's possible that some oil may have coated one of them causing a slight misfire.

This should be a standard question when it's about oil. What brand filter ?

The same happened to me a while back. It turned out to be the sending unit. $28 for a new one a NAPA. Problem has never come back.

Jackhill442 said:

The same happened to me a while back. It turned out to be the sending unit. $28 for a new one a NAPA. Problem has never come back.

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$28 from napa? I just paid $15 from advance last night.

I would also check that it's not coming from underneath your jeep into the engine bay on that side. Mine was doing that when the rear main was leaking down onto the exhaust just under where the engine/transmission meet.