99xjcenturion

Hey I have a 99 4.0 xj but the oil pressure during idle and run is 10 psi unless I give it gas anybody know what's going on?

highmileage

Sending unit may be going out, verify with a manual gauge.

AMCComanche2.5

someone had this problem and posted it in cherokee chat recently. do what high mileage said, but its most likely your oil pump. just replaced mine 1 week ago because i had the same symptoms.

Bustedback

Stop recommending oil pumps for low oil pressure problems. It could be a simple sending unit problem, it could be worn bearings, it could be worn out lifters, it could even be a galley plug that popped out (unlikely). Blindly throwing an oil pump on is not the way to diagnose the problem.

rmoore1031

Good idea. Most people recommend sending units from the dealership. I have a NAPA one and it has lasted a few months already.

hankthetank

i'm pretty sure 10 psi is ok at idle...much less than that and i would worry.

Bustedback

13psi is the minimum required at idle, but who is to say the gauge is not off by a few psi? Then again, is reading too low or too high? Put a manual gauge on it and see what the actual pressure is.

dnuccio

anyone who thinks the oil pump is the problem, read busted's signature.

cruiser54

bustedback is correct in his suggestion. And for someone to blindly suggest that someone replace an oil pump without diagnosis is completely irresponsible.

OP: What brand of oil filter are you using?

99xjcenturion

K/n

cruiser54

Good. Then do what bustedback suggests before throwing any money or time at this.

stang65

yeah it could be alot of things coming together to cause it to do that mine idles really low when she has been being pushed hard but im running 10w30 most the time in it

AMCComanche2.5

hey busted. i am sorry but you're right. I was wrong. I'm back to square 1, still having this oil pressure issue. here are the recent symptoms:

-good oil pressure till about 20-30 min or driving, then it falls to 0-5 when at idle, and goes to dead 0 when on the brakes.

-when i replaced the oil pump, I did everything correctly, but now the oil pan is leaking everywhere, especially in the back. also, the vacuum door under the airbox doesnt work anymore.

I think its gotta be something vith the vacuum system, but I am so confused and dont know what to do.

please help guys, its my Daily Driver and i'd like to fix it before something serious happens

stang65

Have you checked it with a manual gauge?

AMCComanche2.5

no. I can this weekend, but the gauge isnt broken. works fine. gauges dont just break.