Hi I got a 97 xj 4.0l and Ive only had it for about a week and the oil pressure recently started moving a little too much for comfort. When sitting at idle it will drop a little below 40 and when driving depending on rpm will rise a little above, not to 60 or anything. When I noticed this the check engine light came on and I had to replace the O2 sensor. What do you think is causing this, it runs great and I get about 19 mpg with it.

 

mine does the same. I believe it is supose to do that. Oil pressure fluctuates with engine speed.

 

Normal oil pressure should be around 15-20 and 40-50 depending on the weight oil you are using,it is possible your sensor is bad,40 is pretty high at idle. It is possible that the guage is bad also,I doubt it is mechanical,meaning the engine.

 

hmmm well maybe I'll just let it go, but i forgo to mention before than when sitting sometimes when i roll the throttle on i hear a slight tick, not a knock or anything but im using 10W-30 valvoline high mileage semi synthetic oil

 

I run 5w-30 Amsoil and see 40 at idle and 60 at cruise. Runs like a top with 180k. So what you are seeing sounds normal to me.

 

wow 60 seems a little high to me.. the other two cherokees I had the gauge didn't work so I never really knew what they were running at. Do you think it has something to do with the oil pressure building in the head?

 

I didnt think there was a problem with 60.

 

hey maybe your right idk

 

that tick was installed at the factory on the 4.0. lol

 

I had exactly the same problem on my 99 Cherokee. The oil pressure peaked and the needle was pinned on max. I did some looking around, and found/heard nothing. I just replaced the oil pressure sensor by the oil filter.

Everything is back to whats is supposed to be.

 

oh ok well im not to worried about it. Found out today tho that my balljoints are shot...fml

 

They are a PITA to swap out but can be done. Do you have tools? You can rent a press from your local Auto parts store which will help save you time.

Good luck. Let us know if you have any quetions.