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Oil Pressure, Temp, and codes

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Old 11-06-2018, 01:57 PM
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Default Oil Pressure, Temp, and codes

2001 XJ Limited - 151k miles

Well I took the new XJ out for a ride last night and I noticed several things I wanted to ask the knowledge-base here:

1. Oil Pressure - While driving, pressure seems to be between 20-37. If I rev up past 2000rpm, pressure gets to 40. Normailly though, I can cruise at 45-50 and revs are at 1500rpm (is that normal? seems low to me). Engine is not sluggish and responds well to pedal input so i wonder if this is normal on all XJs or if there is something I need to look into. At idle, the needle hovers just slightly above 10psi.

2. Engine Temp - While cruising along at 45-50, engine tem seems to be at around 170-190. The only time I can get to 210 is if I come to idle for about a minute or so. Is this an indication of the thermostat stuck in the open position?




3. Check engine light came on and I plugged in a buddy's code reader. Here's what I got:





How critical are these codes and any recommendations on a fix?

Thanks in advance
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Old 11-06-2018, 03:15 PM
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1 - Oil pressure spec is 13psi minimum at hot idle - 75psi max.
Typically the oil pressure should range from 20 -60 with slightly under 40 being normal for a hot engine under load.

Yours sounds -slightly- on the low side. This isn't necessarily something to panic about. First off - you can't necessarily trust the gauge. If you want an accurate reading, you need to put a mechanical gauge on it. Harbor Freight sells a decent one for like $20. Second - if you haven't changed the oil since you got it, you should (just a general rule). The P.O. (Previous Owner) may have put thinner than spec oil in it or something like that. The Jeep I6 needs old school 10-30/5-30 oil (and not the 0-20/5-20 common in newer engines). If you change the oil to regular 10-30 and it's still low, you can go to 10-40 (slightly thicker) and see if the pressure improves.

Edit - some folks like to put Rotella oil in the I6 (aka Diesel engine oil), so you can look into that if you'd like instead of the factory recommended 10-30.

2 - Temp sounds pretty normal. My 95 runs about 185-ish on the highway and creeps up to 205 or so at idle.

******** NOTE ********* If you are not aware, there is a MAJOR concern with the 00-01 OEM cylinder head. It has a serious casting defect and is very likely to crack. Research "0331 head" and read up about it. You need to know if you have the defective head or not. Low oil pressure, overheating or coolant loss are all symptoms of a cracked head as is "milkshake" looking oil.
Again, don't panic, just educate yourself.

3 - Sounds like you need to replace the 02 sensors (use NTK - the XJ's are picky) and go from there. You should be able to google the code for more info and suggested diagnostic steps. Replacing the O2 sensor(s) is standard maintenance and aught to be done as part of your new acquisition maintenance even if you weren't getting codes, at least IMO.

As far as "how critical" the codes are - if you're running OK and nothing's obviously out of sorts - just take care of the codes as soon as you can. The Check Engine light will flash if it's a critical "pull over and turn off the engine" situation.

Last edited by PatHenry; 11-06-2018 at 03:20 PM.
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Old 11-06-2018, 06:43 PM
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My understanding is the low catylist code doesn't have an operational penalty, just information that it's time to replace the cat.
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Old 11-08-2018, 10:31 AM
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Thanks for the input! I'm tackling a few projects this weekend such as the oil change and a good engine cleaning. Gonna run a mechanical gauge to measure the oil pressure just to be sure and I'll also mess with the belt as there is a squeaking noise when I turn on the AC. After that, I'll take her to a local shop to give it a good tune up and go from there. Now to start looking for the o2 sensors and reading up on the no bus code.

Thanks again, and I welcome any other suggestions/recommendations.
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Old 11-08-2018, 06:41 PM
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Originally Posted by AlamoXJ View Post
Thanks for the input! I'm tackling a few projects this weekend such as the oil change and a good engine cleaning. Gonna run a mechanical gauge to measure the oil pressure just to be sure and I'll also mess with the belt as there is a squeaking noise when I turn on the AC. After that, I'll take her to a local shop to give it a good tune up and go from there. Now to start looking for the o2 sensors and reading up on the no bus code.

Thanks again, and I welcome any other suggestions/recommendations.
You don't need to take it to a shop - just change the spark plugs yourself. There's no cap, rotor or wires on an 01, so what's a tune up - plugs, new air filter maybe?

If you're looking to replace the belt, I highly recommend the Continental Elite belt. (formerly Goodyear Gatorback)... awesome belts and not much more $ than the conventional style. Belt tension on the XJ is way higher than you would expect, so it would be wise to get a belt tension measurement tool if you're at all unsure. I do the twist to 90degree method, but I just read a post that someone said the tension on the 94-96 era XJ (mine's a 95) was more forgiving than the newer ones.
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Old 11-08-2018, 07:42 PM
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Air filter is done and Iíll tackle the spark plugs. I just tightened the belt. I got the krikit II tool and worked like a charm. About 150lbs is what it took to get rid of the squeaking and I have read that the tension in the 00-01 needs to be somewhere between 140-160 lbs.

going to the shop mainly to Change diff fluid, power steaming, brake bleed, trans fluid, and check all the suspension components (the later being my lack of knowledge.

Vehicle le was involved in a front right collision and was fixed, but the tire is running on the fender on that side only so I want to have it checked. I also see some oil coming out of 1/2 shocks.
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Old 11-08-2018, 10:42 PM
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That engine is supposed to have a 195* thermostat in it to maintain that temperature for proper mixture control. In other words, once it warms up, it shouldn't get BELOW 195*. The electric fan cuts on at 215* and runs until the temp drops to 195*.
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Old 11-08-2018, 10:45 PM
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I agree Dave. I suspect that my thermostat may be stuck open. Need to open it up and test it, replace if needed. If thatís not the issue, Iíll be doing some more research! Lol
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