I'm not surprised at your results. Fram filters are junk.

 

I am. My XJ didn't have 40 psi hot idle even on the day I drove off the lot with 10 miles on the odo. Something is obstructed somewhere...

 

I'm talking about the increase in pressure. Who knows about the accuracy of these sending units.

 

I have mine mostly all back together. The sending unit needs to be replaced as I know it has good rods and mains in it but is still fluctuating above 40 for no apparent reason. Shoots to above 50 and then dances around 40-42 at cool idle. Can't really say what it's going to be like in short order as I still have yet more work to do on the thing. But the main bearings were much easier to change on this than any other engine I have done. Will post results by the end of the week.

 

I'm going to bring this thread back for a while, I have a very similar problem to all of you above, I have had it for a long time but it is slightly different.

Note: As of right now I have not replaced anything, but i plan to replace the oil pressure switch this weekend.

My oil pressure at hot idle almost always drops down ALL the way to zero, and the check gauges light illuminates. It has done this on and off since I bought the Jeep 2.5 years ago, but everyone i spoke to pointed this to a bad oil pressure switch and assured it was nothing to worry about. When I am accelerating or cruising my pressure is around 30psi and is steady, but as I slow to a stop at a light or something, it drops rather quick and hits zero. As soon as I accelerate it goes back up. Once in a blue moon the Jeep will start and run rough for a few seconds until i give it some gas. I want to say it only happens after the engine is hot (Like i drove to the grocery, and when i came out from the grocery it starts rough).

Now i have some money to spend and wanted to go around and fix little quirks, like the oil pressure switch and the 4wd indicator switch, ect. I just wanted to see if anyone thought that having zero.

I do have a fram tough guard filter right now and penzoil 10w/30 oil, but I am going to change the oil today since it is nice out. My oil level is currently in the safe zone but it is a bit dirty. I have used Fram filters always, not really knowing better, and this has always happened but not quite as much as recently. Also I have put 1/3 can of seafoam in my oil a few times, maybe every 3rd change, though i am not sure if this helped much if at all.

If it does not turn out to be the Oil pressure switch, is there any possible way to clean the Oil Pump or Oil Pump Screen to get improved oil pressure without completely replacing them?

Also what other kinds of oil/oil viscosity, oil filters do you all recommend?


Update: I will be trying the fix at this link tonight when I am home from school.
http://www.jeepforum.com/forum/f19/4...fixed-1304679/


Thanks!

 

Sounds like your pressure sending unit. Actual low pressure will be extremely obvious at idle. No pressure implies to lubrication - you'd hear one hell of a knocking and scraping at idle.

First step is to rent a mechanical oil pressure gauge and verify what your pressure actually is. Sometimes there can be crud blocking the passageway to the sending unit. These are reponsible for probably 95% of "low oil pressure" complaints.

As for oil there about nine thousand threads on this subject, mostly people stating what they run. If you want to educate yourself with facts read this: http://www.bobistheoilguy.com/motor-oil-101/ My recommendation is to run whatever makes your Jeep happy. If it's cold where you are, run a 0W## or 5W##. Otherwise most #W30 and #W40s are fine. A lot of people here swear by Shell's Rotella - I run T6 5W40. It is a very highly regarded oil, but may not be right for you. Each 4.0 acts differently so experiment!

As for filters you get what you pay for. The orange FRAM and other filters in that tier are junk. WIX, also sold as NAPA Gold, is a well priced, quality, easily available unit. Purolator PureOne and Mobil1 are fine choices in the upper end. More here: http://www.minimopar.net/oilfilters/index.html

 

Well today I poked around in the old oil pressure sensor with some pipe cleaners, got a little gunk out and also removed the 90° hex thingy and cleaned it. I then put it all back together and changed my oil and filter, I used a NAPA old filter in place of the FRAM and valvoline 10w30 high mileage.

It ran real nice for most of tonight, the oil pressure idled at 20 and at accel was about 35 and I feel like it is so much more powerful now than it was this morning, better and stronger throttle response. but as I was pulling into my apartment coming home from my girlfriend's, the gauge dropped back down to zero and said check gauges again. I'm assuming its the oil pressure sensor, and I will be purchasing a new one online soon

 

1st you have to verify with a mechanical gauge.
2nd: In most cases low pressure is caused by less restriction to flow, in other words...worn engine.
3rd: 30 psi at cruise is more than adequate low pressure at idle is not important unless it is ZERO ( in which case your lifters would collapse)
4th: As engine wear increases PSI goes down BUT oil flow INCREASES, it is flow, not pressure that lubricates the engine
5th: If you can see oil flowing under the oil fill cap at idle you are ok
6th: If it ain't knocking just keep rocking.

I would recommend a 15w40 diesel oil like Rotella,Delo, or Wally Supertech and NO additives. Be aware of this condition,allow motor to warm up when cold, drive easy,record and benchmark your pressure/temperature readings and noise level. You said you had this condition for 2.5 years? You will probably be fine for a good while.
If things turn south you can always rebuild. Believe me, low oil pressure is common on the 2000 & 2001 4.0s and it doesn't necessarily mean the end of the world.

 

Thanks for the help! I plan to see if any of my buddies have a mechanical gauge I can borrow. If not, I will find or rent one from somewhere else. Just to double check. It has been happening for quite some time and the jeep is still kicking so I am not overly worried. Just one of those browsing-the-forums-turns-you-into-a-hypochondriac things.

Honestly the reason I was searching around is because it seems like the Jeep (when it reads zero oil pressure) runs a but rough at idle, and Idles lower than 750. There were a few times in the past month where it idled somewhere down near 300 or 400 and felt like it wanted I stall, but I attributed this to cold weather, and now also to that ****ty FRAM oil filter, because it runs a lot better now.

I was always slightly skeptical that since I have an 01 that the head may be cracked or be at stong risk to do so and that is what was causing this problem, but I have seen no signs of this issue, I have never had milky oil or grimy coolant.

 

Important info!! you may not have a oil pressure problem at all. If your engine is running rough and idle speed is low your OIL PRESSURE is going to be LOW too!! Check to see why your engine is running so rough first. Low oil pressure will not cause this UNLESS it drops to zero and collapses the lifters...in which case you will HEAR loud tapping sounds.

 

Simple thing to do for low idle, and it's considered maintenance, also. What brand of oil filter do you use?

Courtesy of TJWalker:

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The Idle Air Control (IAC) is mounted on the back of the throttle body. (front for 87-90) The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is moved in, the air control passage flows more air which raises the idle speed. When the valve plunger is moved out, the air control passage flows less air which lowers the idle speed. Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea.

CLEANING THE JEEP 4.0 IDLE AIR CONTROL

Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a torx driver (2 bolts; one can be kind of hard to get to)

"Gently" wiggle out the IAC from the throttle body. Gasket on the IAC can be re-used if it is not damaged

Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and is best for this task. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.

Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner

It is also a good idea to clean the entire throttle body itself, the butterfly valve inside of the throttle body and all associated linkage as long as you have things disassembled

 

Thanks for that info! I have both cleaned and then replaced my IAC valve, and it did not help with my intermittent low idle problem

 

My oil pressure gauge shot up to 80 two or three times today for no reason, that was pretty strange but it has to be because it's busted. I did see oil in the contacts for it and cleaned it out but nothing has changed yet.