I must have said/did something my WJ didn't like. I get half way to work this morning, stop at a red light, and my oil pressure gauge plummeted. If I keep the car up at a high idle, it will stay in the middle. Has anyone replaced one before and have any advice? Or maybe you had the same problem and something else was the culprit. I have changed the filter, and the oil is right at the full line. First the trans and now this... My xj naver gave me this much trouble and I beat the hell out of it.

 

Replace the sending unit, before ripping into the engine.

 

yea mine does that too i realized it was the sender when i drove like 100 miles with the oil pressure at 0...the sender is cheap and its an easy swap

 

same problem with my ZJ exept oil pressure tappin the 80psi mark. changed the sending unit and problem solved. should be easier for you than my 5.2, they are a PAIN to get to

 

yea the 4.0s are right below the oil filter and easily accesible

 

id say it is so lol
mine does the same thing replaced the sending unit to no avail just waiting till i smoke the engine
then il drop in a LS1 and be done with it

 

Agreed. Not expensive or hard to replace if you've got the 4.0.

 

Will try replacing the sending unit this weekend when I change the oil. I hope that does cure the problem, but the gauge doesn't act erratic, it moves with the rpms. Whenthe rpms drop so does the pressure. I had this problem on my XJ only, the gauge would go from normal to bouncing off one side to the other.

 

What oil weight do you run?

 

As a rule of thumb, you should have close to 10psi of oil pressure for every 1000rpm. As long as you have that, you'll be fine.