Need advice on engine making a new sound.

[Magdump]

I have a 97 Jeep XJ. I replaced engine about 1500 miles ago with a remanufactured engine. It has been the quietest 4.0L I've ever heard. It didn't have a click rattle or knock since it was installed. Recently when the engine was at idle with 55 lbs of oil pressure you can hear a deap bottom end knock like a rod. It has never been hot and I only run Lucas high zinc 10w30 oil and Wix filters. I've changed it 3 times in the 1500 miles. I'm not confident with all the cheap Chinese parts out there. I've seen so many cams and lifters eating themselves alive. So far I hadn't seen any metallic specs in the oil. Im going to start unplugging injectors one by one to see If it changes anything. Has anyone had this problem? Do some 4.0Ls just make bottom end noises?

[mpgMike]

Your idea of disconnecting the injectors one at a time is a good one. It will help you try to isolate if the noise is a specific cylinder that knocks under even idle load. You can also use a stethoscope to narrow down where the noise is coming from. You can use a really long screw driver, placing one end on the suspect spot while pressing your ear up to the handle. Louder noise means you're closer to the source.

[Magdump]

Thanks for the reply. I'll be sure to give it a try.