[jdl71]

I recently purchased an '05 z71 5.3, 204,000. Had a noisy tensionser and water pump, replaced those. Also had a code on for knock sensor fault, so I pulled the intake, replaced both knock sensors and connectors. Now the engine has developed a knock, sounds like it's in the bottom of the engine and similar to a rod knock, but it won't do it until the engine is up to temperature. I also don't hear the usual "flutter" or whatever it's called when you rev and let off like a rod or bearing will do. I've been all over it with a stethoscope, and can't seem to get it pinpointed, other than it does seem louder on the oil pan than on the top of the engine. I can also hear it better on the right exhaust manifold than the left, can hear it right where the bellhousing meets the block, but not so much under the torque converter. It also will go a way if driven at highway speed for a short time, then returns after idling for a minute or two. I've pulled each plug one at a time to kill each cylinder, no change. I'm really at a loss here, maybe a wrist pin? It does increase with engine speed while revving the engine when parked, putting in gear, holding the brake and revving seems to make it go away although it's hard to tell for sure as it's not really that loud. Two other things of note, when I pulled the intake there was oil in it, however I've read this is a somewhat common problem with the PVC getting plugged or valve cover baffles getting plugged up. Occasionally when first started I will get "oil pressure low" on the display, but the gauge reads fine, and no abnormal noise. Other than that the truck runs wonderfully, and I've always thought the LS motors would run forever with basic maintenance. I don't know the truck's history for sure, but it was a one owner vehicle when I bought it so I would think whoever had it that long would have taken decent care of it as the body and interior and immaculate.