Swlippelt

4WD4EVER

Get your hands on a mechanical oil pressure tester, < $20 at HF, and check it with that. You may also want to consider a compression and leak down test.

tjwalker

White smoke can indicate burning of "coolant". Check your coolant reservoir; is it down to a level that would require adding some?

I would park it for now and do some basic testing as 4WD4EVER recommended. A simple compression test can often diagnose a blown head gasket which is a possibility here. Verifying oil pressure with a mechanical gauge will tell you what your true oil pressure is.

The compression spec for the 4.0 is 120-150 psi, with no more than a 30 psi variation between cylinders.

The oil pressure spec for the 4.0 is as follows:
*Not less than 13 psi at HOT idle
*Between 37-75 psi over 1600 rpms

Good luck and keep us updated on what you find!

PatHenry

Sorry for the sort of off-topic and possibly naïve question - but the statement:

-- is this like a "shop-talk" convention or something to specify that there can be no more than 30 psi variation?? Why even mention variation?

As far as the 4.0 spec, isn't it completely redundant to mention that the variation can be no more than 30 psi. If all the cylinders are within 120-150, then they are automatically no more than 30 psi different and conversely, if the variation between cylinders is more than 30, then there is at least one cylinder that has to be outside of the 120-150 range. Right?

I have to assume that since folks always mention the compression as between X and Y with no more than Z variation, that there must be engines that have an acceptable range of like 120-200 or something, but the variation can be no more than 40 between cylinders. In that case, obviously you could pass the first requirement, but if Cyl 1 was 120 and Cyl 2 was 180, it would fail the second requirement.

Sorry for the sort of dumb question, but it always seems strange to me.