Thanks for the quick replies! Here are some answers to your posts AND the dealer's diagnosis...
Does it make this noise in neutral or park as you rev the engine up?
I don't think so, but will check this evening and report back.
Does the knocking speed up with revs or does the knocking stay at the same constant rhythm?
There is no discernable 'rhythm' to it that I can hear.
Does the noise vary with speed of the vehicle or speed of the engine? Are there any vibrations or 'wobblings' felt?
Yeah, that's what's most perplexing to me. When I accelerate quickly from a dead stop (relatively high rpms), I don't hear it. Only at higher speeds
You did say jeep right? Don't they all sound like that?
Actually, while it's no Benz, I'm generally quite pleased with its combination of comfort and off-road/nasty conditions capability.
Is it engine pinging or some other metallic knock? As you know engine pinging in a modern engine would result if the knock sensor was defective and did not retard ignition timing properly when lower octane fuel is used or the EGR valve fails closed.
Knocking can result from gummed up hydraulic valve lifters, but that is usually evident upon startup.
The first thing that I thought was that it was pinging and simply resetting the timing/ECU would set it straight. The dealer checked it and said it's not the timing.
<Kinda funny, kinda scary--the first time I mentioned it, the dealer said, "Use Premium gas." I replied, "The user manual specifically states not to use premium in this engine." I was right.> I only use Esso gasoline, so it's not El-cheapo brand gas.
OKAY, the service manager at the dealer, after riding with me and checking it out in the service bay for about an hour, said that it needs the lifters and rocker arms replaced. What do you guys think of that?