I have a 1993 jeep Cherokee with a 4 liter inline 6 cylinder engine and my oil pressure is consistently very high, even though I just changed it. What could be the cause of that? Also, I think one of my cylinders is misfiring and the check engine light is on. Are these things related or are they separate problems? Could my check engine light be indicating another, less noticeable problem?

 

They are not likely related.

What do you mean by high oil pressure? The oil pressure spec. for the 4.0 is 37-75 over 1600 rpms and not less than 13 psi at HOT idle.

First, check the connector leading to the oil pressure sending unit. Right above the oil filter. Sometimes they get knocked a bit when you are changing oil. If that is good, then I'd recommend you TEST your oil pressure. Must be done with a mechanical oil pressure gauge temporarily installed where your oil pressure sending unit. Then you'll know for sure if the pressure is high or if the sending unit is the likely suspect. You can often rent a mechanical gauge from parts stores; call around. Or any shop could do this for you inexpensively. Some might just say replace the sending unit as it is a common fail and you could do that, but I always recommend testing.

As for the check engine light, below is how to retrieve the code. Very easy! Post the exact code here for comment.

If you have a misfire, when was the last tuneup? Fresh Champion copper plugs, quality spark plug wires, distributor cap, rotor and fuel filter. The importance of fresh tuneup parts cannot be overstated.
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Retrieving OBD codes on the Jeep Cherokee (XJ) OBD1 Models: 1991-1995

1) Start engine (if possible). Move transmission shift lever
through all positions, ending in Park. Turn A/C switch on and then off
(if equipped).

2) Turn engine off. Without starting engine again, turn
ignition on, off, on, off and on within 5 seconds. Record 2-digit
fault codes as displayed by flashing MIL.

3) For example, fault code 23 is displayed as flash, flash,
4-second pause, flash, flash, flash. After a slightly longer pause,
other codes stored are displayed in numerical order. When MIL begins
to flash fault codes, it cannot be stopped. Start over if count is
lost.

NOTE: A "5-5" will always occur to signal the end of the sequence. Some will flash the "1-2" code indicating a recent battery disconnect even if you haven't done it. Ignore these two codes, and mark down all others.

 

Check the engine codes

http://www.jeep-xj.info/HowtoECUcodes.htm

 

I did that, but for some reason when I did, the piston stopped misfiring, the oil pressure dropped, my exhaust stopped billowing smoke, and the check engine light just turned off without giving me a code. I'm so confused and worried about what just happened. Do you have any experience with a car just randomly working fine after trying to get a code?

 

Sound to me like it's fixed.

Dont worry, be happy.

My refrigerator has been leaking for a week now, everytime the icemaker solenoid clicks over, I had a splash of water on the floor. I have been busy, so a towel and the shut off valve has been handling the issue until I get time to fix it.

Guess what I noticed today? that silly thing is no longer "leaking". ( I suspect an errant bit of Ice was messing up the operation, but I am not going to start taking things apart that are working).

you may have had some junk accumulated on a sensor or some other non-repeatable issue.

Be glad that it "fixed itself". this seldom happens, but it is wonderful when it does.

 

Thank you so much!

 

Just curious, how high was it?

I have a bout 6,000 miles on a rebuild and I idle at 40 and go from 40-60 while driving.