Anyone ever have problems with there engine losing oil pressure after 4.0 engine swap. I think the filter might be pluging. I have changed the oil twice now. The motor had tons of slug in it when I did the swap. I pulled the head off cleaned it dropped the pan cleaned it. Im going to go change the oil to more times today. The motor was a 2000 the head is a 92 its in a 1997 xj using all the hook ups from the 1997 .seems to be running fine Thanks for you time and help

 

Might have gotten a bad motor. Doesnt sound like it was taken very good care of by your post.

 

What's the stock oil pressure supposed to be at idle? The motor has 120 k on it and it sounds fine. I've changed the oil 5 times now and it seems to be getting better. Oil pressure is holding at 10 lbs idling? There seemed to be allot of metal in the oil at first, but that's getting less and less as I change it.

 

Now im thinking oil pump may be bad. Were going to change out the oil pressure sensor tonight to see what that does. Any advice?

 

Oil pumps do not make pressure, resistance to flow makes pressure. You could have one of two things going on here. #1 could be worn main, rod, and cam bearings. Excessive clearence between the bearings and journals will cause the oil pressure to be low, the only fix is to replace the bearings. #2 could be sludge build up clogging the oil pump pick up screen and causing the pump to starve for oil. Less flow equals less pressure. Or you could have all of the above happening.

 

So are you saying the pump doesn't go bad? I changed the sensor today and its still has low pressure I gonna try and run some sea foam and change the oil again. If that don't work im going to change the oil pump. But from what the last guy said that wont do anything? ??? Anyone with some advice?

 

Pull the oil pan off and take a look inside at the oil pump pick up and pull a cap off and inspect the bearings.

 

What brand of oil filter are you using?

 

X2 certain oil filters have effects on pressure. IE I used to use STP filters on my 258 then switched to a Purolator filter and the pressure increased a little. It has a lot to do with the material and design of each filter.

 

OP: So what brand of oil filter are you currently using? It's not orange with black trim , is it?

 

this is never a good thing. As already mentioned check your bearings.
Hopefully you haven't got a screwed up crank.

 

youre on the right track with the oil pump but more importantly, change the strainer on the bottom... they are usually the culprit in a sluged up engine... it would be well worth your time and money to go ahead and replace the pump while you have it apart tho

 

sounds like when my cam and main bearings went out in my 2000.... started getting low oil pressure issues at 130k. when I rebuilt it, the crank was worn, and the cam bearings where worn in an oval shape. Rod bearings looked good. I would bet you have excessive bearing clearances, if you pull a cap use plasti-gauge to check the clearances....

 

Ok so I just went and grabbed it from the shop. It started out ok. The pressures were up around 35 as I was driving it and 10 at the stop lights. But after about 5 mins of drive its at 0 at the stop lights and 10 while driving. I can get it up to around 20 when I step on it. But I think I have no pressure. When its parked the motor sounds like its running smooth. No tics. I think it needs a pump and not the bearings. Im thinking about changing the pump tomorrow.

 

good luck, cross your fingers. I made mine get my by about a year running 15-40w oil to thicken it up and it helped with it dropping to 0 when warm at idle. but it doesn't fix the problem, I did this after replacing the sender, and pump/pickup.

I would still check bearings while you have the pan off. when there is metal in the pan the first thing to go are the bearings...