muddeprived

10 psi at idle, 40 at highway speeds. As soon as i come to a stop, it drops down to 10 and gets a tad bit rougher. It doesn't cut off or anything. I went to see my buddy today and noticed it hanging around 10 at a light. I stopped at the store and when i restarted it, it was running rough and shuddered a little when acclerating and had little power. I restarted it and it was fine. It still hangs around 10 psi at idle.

anyone familiar with this?


2001
4.0
84k
recent tuneup
oil level normal

Bastard Child

find a product made by bg called moa and use it. might be a dirty oil system or a clog. worst case might be your oil pump maybe going bad.

Bastard Child

muddeprived

I need to test my oil pressure first. What mechanical tester can i get? I never seen one nor know the exact name for it. How much are they?

BonesJackson

10 psi at idle isnt all that bad really. Oil viscocity may play a roll too with the pressure situation. I run 5/30 in winter and 10/40 summer. As metioned below a weak oil pump is always a possibility as well.

Now, the driveability problem. Is the check engine light on? If so have a local Autozone check for a code. That light is actually quite helpful.

muddeprived

No light. I have a check engine light tester. Something has to be off, even though the pressure is within specs. Since i bought it, it has always stayed at 40 psi most of the time and sometimes climb to 50-60. All of a sudden is drops to 10-20 at idle and runs just a little bit rougher. I changed the oil two months ago with 5w-30 mobil oil and purolater filter. I also poured in a can of that engine restore while i was at it. The previous owner didn't change the oil much at all...if ever. Would that can of engine restore thin the oil out?

Bastard Child

My best guess would be try another oil change and see what happens.

Bastard Child

Kyle

X2 i would also try another oil change with a new filter. try a bosch filter.

sometimes the filter can throw off the reading.

also i wouldnt 100% rely on the gauge on your dash they are known for not reading correct. if you are that worried get a direct reading of your pressure.

-Kyle

muddeprived

Aye, i'm gonna try that first. I was about to go buy another sending unit but decided to wait and change the oil. Any particular weight to try? I use 5w-30.

This is the 2nd engine related issue i've had during my 12 years of driving so engine stuff is all new to me. Both came from this same xj.

86 f-150 = no issues for 8 years (dad's)
89 oldsmobile 98 regency = no issues for 6 years (mom's)
94 oldsmobile cutlass supreme = no issues for 4 years except a battery swap
2000 dodge dakota (muddy one!) = no issues for 4 years
2000 jeep TJ = nothing for 4.5 years
2001 XJ = 2 motor issues in the 3 months i've owned it.

Hopefully i don't get a chain-reaction of problems.

Kyle

i believe the book calls for 10w30 and that is what i have been using for the last 30k with no issues at all.

-Kyle

muddeprived

Thanks i'll switch over to that using Mobile 5000.

Kyle

FWIW i have been using Castrol GTX for every car and every oil change i have ever had and never once encountered a problem.

just figured i would throw that out there.

-Kyle

vistacruiser

Mine does this too .... actually fluxuates between 40 and 10 psi or less sometimes even at speed. I know the OP is not that low or the engine would be heating and the lifters would be rattling. My second new OP sender is in my glove box .... a replacement fixed the first time. I'll put in my vote for the sending unit

Captainkirk

This is exactly the problem I'm going through with my '91 Briarwood right now (180k) It started out just like yours and advanced to the point now where if I drive more than 5 minutes the oil psi drops to ZERO at idle. Putting it in neutral and holding the R's up brings it back to 18 or so. But basically I've got a car with a 5 mile range. My research detected this is a common problem...lose the oil pump between 120 and 150k....apparently it wears out...I'm going to dig into my motor in the spring and either replace it or overhaul it. My suggestion would be to get a new oil pump, pull the pan and change it out (which is what I shoulda done last summer). My motor is a 4.0L H/O.....is that what you're running?

muddeprived

4.0 non-HO. I've been drivng it around lately and it has only dropped to about 20. Not much i can do at this point in time due to the weather so i have to hold it out until it warms up to diagnose/fix my issue. It's running fine though so i'm not really worried...yet.

Captainkirk

My opinion......get worried. Make plan for warmer weather and carry thru 'cuz it will get worse. I wish I'd listened to my own advice.