Heu everyone! I went on a trip through the mountains recently and I noticed that when I rev'd the engine between 3 and 4k RPMs the oil pressure dropped from where it normally sits at 40 to way down around 10. Has anyone experienced this before? Where should I start to fix this? I have the '98 4.0L Sport.

 

The oil pressure spec for the 4.0 is 37-75 psi over 1600 rpms and not less than 13 psi at hot idle.

The first thing I would suspect would be an oil pressure sending unit starting to fail. It's a very common failure on the 4.0 engine. If it drops out in a specific range, I really would suspect the sensor more than an actual engine problem.

If I were you, I'd install a new MOPAR oil pressure sending unit purchased from Jeep and see where you are at. I'd go MOPAR for best accuracy/reliability/mating with your factory gauge. Not that expensive and easy to install.

Good luck and keep us updated!

 

First,I would rule out the sending unit by replacing or installing a test gauge. A loss of oil pressure with an increase in RPM usually indicates a clogged pickup screen.

 

Had this exact same thing happen and it ended up being my OPS. If your engine isn't making any funny sounds, odds are its the OPS

 

Awesome, thanks for the info guys! I'll give the sending unit a shot, then go from there.