hey guys, not too good at this jeep stuff yet but im learning! recently ive noticed that my oil pressure is running at about 1/4 at idle but when i accelerate it goes up to the middle to 40. When it starts cold, the oil pressure is at about 40 to a little more and doesnt move past there on acceleration, its when the car warms up and idles that the oil pressure drops to about 1/4. Also when i go to start my truck after the idle pressure is low the truck takes about 2 turns of the key to start. What could this problem be? Maybe an oil pump going bad? help me out guys!

 

as long as you have 10 psi for every 1000 rpms you are fine. its not uncommon for a jeep 4.0 to have low oil pressure at idle

 

ok so there is no need to worry then?

 

My 99 does the same thing. I have had it 5 years and its never been a problem.

 

what weight oil you running? try changeing to a heavier weight.

 

you'll be fine. my 99 has 15psi at idle 20 50 mobil 1

 

If u had a shop/mechanic verify oil pressure with a accurate test gauge, u would really know if there is no need to worry. Don't try to change/munipulate oil pressure by using thicker oil. Thicker oil runs hotter and robs power.

 

20-25 psi at idle is what I have gotten every since I owned the ol XJ. When you're driving, you should get about 40-45 psi if you're going interstate speeds (2250 or so rpm with my AW4). ALL NORMAL. No worries. When you start hittin less than 15 or so psi at idle, start checking stuff. As for warm up, it depends on how cold it is, but normally it will be around 60 psi at idle and slightly over while driving until the oil heats up and becomes more viscous.

 

That's actually normal. 1/4 on the indicator is about 20psi, which isn't bad for warm idle oil pressure on a used engine. According to the Haynes manual, 800RPM should be around 25PSI, and above 1600RPM should be ~40PSI. So your right there around where you should be.

As for the 2-turn start thing when hot, have you given it a tuneup recently? Check the air filter to make sure it's not dirty, and run some fuel injector cleaner through it (I recommend Lucas, it's a bit more, but it works). Also verify your engine grounds are good, there should be a ground strap at the back of the head, you may need to remove it and make sure the connection is metal-to-metal.

 

it becomes less viscous

 

i run 10 30 mobil 1 and i will check everything, a tune up is probably needed seeing as the PO didnt take much care of it.

 

I know that the SCIENCE says you should have 10 pounds for every thousand RPM...but that seems awful low to me. If I had 20 pounds at 2000 RPM, I'd be uncomfortable. I don't know why...but I would be. Again...I know the science says "relax" but...

And I know it also goes against the science to use heavy weight oil to improve oil pressure but there is something about "low oil pressure" that keeps me awake at night.

My XJ drops to 20 at idle and just over 40 at cruise when hot. I'm OK with that. I just don't know what it is about oil pressure that bothers me. It just seems like I want 60 pounds at highway speeds AT LEAST. I think I'd actually feel better if the gauge lied to me...

 

oops, my bad. Cant believe I missed that. Thanks

 

You will learn to hate your XJ's previous owner further down the road then lol.

 

should i change to a different weight oil? and if so what weight?