Long story short I got my 1997 Jeep Cherokee XJ 6cyl auto from a friend who barely performed the bare minimum maintenance, I had helped him purchase the xj from the original owning family but their maintenance records were pretty much non-existent and the jeep had some ghetto fixes on it (ex: the hood release cable snapped the the guy ripped out all the hood latches and installed hood pins, badly I might add)... I've been fixing it up and replacing practically everything since I got it in October (and I mean EVERYTHING).

In reference to this post I have replaced: valve cover gasket, PCV and Breather valves on valve cover with grommets, both vacuum and fresh air lines, oil pan gasket, rear main seal, oil pump, oil filter (high quality but had been sitting in its box on a shelf in my garage for about 1yr or so), 5 qts good quality oil w/ 1 qt lucas oil additive. The oil pressure sending unit I had replaced for my friend when he owned it.

The jeep ran and drove fine with all the PCV stuff changed but I noticed that my oil pressure was well below what my 95 YJ (same engine) has normally and one day while in heavy traffic it was reading almost 0 and hovering between 5-10 and I had to keep the engine revved to keep the pressure up. As soon as I got home I performed the Oil pump, rear main, and gasket swap. After that I swapped out all of my tranny lines and installed a cooler and filter. I noticed my pressure was equal to that of the YJ but still increased a bit with RPM (around 50 at idle). Then I noticed the rear of the valve cover was a bit wet with what appeared to be clean oil but figured I might have done that when adding tranny fluid, so I quickly re-torqued the rear valve cover bolts. After a test driving it last night I noted that the oil pressure did seem to increase a bit but nothing over 70... then today the pressure went up to 80 twice with rpm....

Any ideas what could be causing this problem? It seems like every single time I fix something, another thing goes wrong


Forgot to add that I also replaced the distributor at the same time... when I did so a little bit of engine grime fell down into the hole...could that be causing a clog somewhere?

 

CHECK WITH MECHANICAL GAUGE

Playing around in there and doing all this work, you could have easily knocked it loose, or it failed, or it was loose, and you knocked it back in to place, whatever.

They are pretty inaccurate anyway. If it was sitting around 10 at idle, your likely fine, especially if you don't have any lower end knock.

The minimum PSI at hot idle for this engine is 13 psi. Even though yours read 10, it could just be off by a few (Very likely).

Check with a mechanical gauge to see if it is actually as high as your dash says it is...

If it IS actually that high, im not really sure what it could be... Maybe wrong oil pump?

Somebody on here is sure to have more info for that part, but seriously take into consideration the starting point i have thus presented you, good sir

 

The pressure relief valve in the pump could be hanging up. I've seen trucks blow filters apart because the valve stuck. Put a mechanical gauge on it and see what it's doing.