Ok here we go. I just bought this yj 150 k on it. I test drove it and it wasn't noisy. The pressure wasn't great but not bad , it was about 40psi and quiet well for a 4.0. I drove it home on the freeway and now it's only getting 35 at best. I changed the oil and now it sounds like a diesel. I'm very flustered because I just brought it home. Think the guy knew ?
Help!!!! Thanks
This answer by Gunner speaks to my experience.
My oil gauge played with my head for a long time.
I'm not saying your jeep performance is playing with your head.
I'm saying my oil gauge played with my head.
Mine was always 15-20 lbs. WTF I thought. These are $12 parts with a lifetime guarantee where I buy my parts. I went thru 5 of them. You ever have your engine leak ALL of its oil from the TOP??!! Mine did twice. Blew my mind.
Long story short. I've never had a good history with oil sensors. 5 in 7 years of ownership. They are probably built out of this country. When the sensors did work for me I felt the readings on the dash were too low then the disintegrated. Current one I had for 2 years. 5th time was the charm I guess..performance is maybe affected by crappy sensors, but not always. After reading your post 3 times I think dieseling and your oil pressure are unrelated. Dred has a great point with viscosity and nubby is on to something too.
For what its worth...It's quite likely I'm 100% wrong and I have nothing to offer this thread...but sometimes it is the little things.
I'm having the exact same thing goin on on a 91 yj with a stroker 4.6l. I have literally torn the top end down to get to the bottom of it to no avail. My engine is not new but the original block, bored 4.2 crank, stock cam new valve train and all. Broke in properly, ran perfect for 2 yr, then after an oil change, got the nasty taps on just #3 intake. Lifters good, pushrods good, rockers good oil pressure great. No miss gobs of power, just taps till its good n hot, then spuratic after that, but like it turns off, then on. Currently, well at lunch at work today, dumped the 300 mile old 10w30 Rotella in it and put in 5-10 oil to see if there was any change, it quit tapping all together once warmed up. So I'll see how it goes tomorrow, in my daily traveles n let you know. Fyi it was 80 here today.
Good luck OV. I'm just worried Ive bought a bad motor. I'm willing to do what I need to do. I'll put mains and rod bearings in it to get more life out of it. Just think it's odd that I'm not getting the 40 psi I had when I test drove it.
Look the engine over very close, and see if any of the Valve cover bolts have been removed and installed and on the Oil Pan too, if you can see a new Gasket on any of this, look for signs that someone has been into the engine, if all looks old like no work has been done lately then the PO may not have tried to Mask a problem, and it is just something that has come up. Down here we have a law that gives you 3 days to bring it back and demand your money back.
I was under it last night and all the bolt were covered in dirt so I'd say it hasn't been messed with at all. Same with cable cover. He really didn't clean it up at all. I mean if this did t happen I think I got a good deal. And here's the listing.
1995 Jeep Wrangler. Rough Country 4" lift, 33" BF Goodrich all terrains, have good condition 33" BFG spare, 4:56 gears, Dana 44 rear axle with Detroit locker, Lunchbox locker in front. Red full length spider webshade. JCR offroad rear bumper, but no tire carrier. Good condition hard top with racheting hoist for garage storage, and soft top included. Has sound bar and Pioneer radio. Starts and runs good but the synchros are worn and causing the gears to grind a bit when shifting into third gear, but does not pop out of gear or grind once it is in gear. Spare AX15 transmission included to fix the issue. Perfect setup for Michigan wheeling.
My Yj 4.0 with 170k and my old yj 218k both would and still do every time I turn it on oil pressure starts at 40 PSI and as the engine warms up pressure drops down to just below 20 PSI. Every day . no egine noise . I used to worry about it, but the temp never goes over 190 . so I just live with it.
Its rare to see a jeep 4.2 or 4.0 without lifter noise. Use whatever oil you want. I dont want to start a oil thread here. I use sae 30 in summer 10w30 late fall through spring. The thicker the oil the harder it is for the oil pump pressure to push it under the bearings, and through small passages like the lifters and pushrods. New lifters are a crapshoot as everything else now. I have taken new lifters and hand pumped them in a coffee can of oil . Standard practice . Installed them primed motor with a primer and half inch drill in distributor hole for 1/2 hour. Sometimes still had to tear back down due to one not wanting to pump up. As far as pressure it will drop some after warm up. As a rule of thumb 10 psi for every 1k rpms is just enough to keep a motor alive . I run a mechanical guage . 60 psi cold at idle 45 hot idle . With sae 30. climb's with rpm as your spinning oil pump faster. Thats a 12000 mile 4.2 with stock pump . Anything less than that with them parameters is showing you how wore the bearings are.
My Jeep guru told me 10 lbs oil pressure for every 1,000 RPM is adequate for a 4.0L to run normally. I am on my third 4.0, with the last one having over 180,000 miles and still go strong when I sold it. My current one is at about 50,000 miles. Just like all the others, mine shows oil pressure 20-40lbs. Sometimes on cold mornings and some hot afternoons it sounds like my Superduty 7.3. It must just be the nature of the beast because it's still running great. I have come to realize most of the problems I suspect are in my motor are probably just in my head. Actually, I have never had a major problem with any of my 4.0Ls . . . . .yet
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