Originally Posted by 2fas4u
I also have 150K on mine and I hear what your hearing when going up a steep grade hill. Sure sounds like detonation or knocking to me. I know if the timing is off slightly the 4.0 does not care for it. Im not sure what your hearing is timing chain rattle....
I'm not sure either. I've heard knock before in other vehicles, and that's what this sounds like. But you guys have a lot more experience with the 4.0 (I've had 3 4-cyl Rangers) than I do. I've also never known detonation not to at least improve with higher octane fuel, and this noise doesn't change at all going from 87 to 91.
I'm reading up on some of the posts here about using Seafoam to clean out the combustion chambers, and I may try that for good measure. I might also look into checking the timing based on your comment about the 4.0 not being tolerant of it being a little off.