I've had rides in non-Mopars that had rod knock. Excessive rod or main bearing clearances have a fairly disticntive sound to each. If it was a damaged bearing, I would think you could have a low oil pressure light issue when fully warmed, at idle in high ambient temps.
While my '93 Grand Caravan w/3.3 V-6 was quiet even with 100,000 miles, our 80,000 mile, '05 Caravan SXT w/3.3 V-6 I now have has more like a "rattle" or "slap" coming from the passenger side (front of the motor).
I'm assume an advantage of having both camshaft and crankshaft position sensors is (also assuming the PCM software supports) the PCM should be able to detect "excessive" chain stretch/wear via an inconsistent cam to crank relationship.
The 1965 Chrysler New Yorker we had with the 413-4BL RB motor at 145,000 miles showed a large variation in ignition timing (degrees of advance). Since it was the original silent type timing chain, I assumed it's chain was pretty loose. I don't remember if the front of that motor was noisey (knock, rattle, etc?) or not.
The knocking is in fact a "slapping" sound. It is intermitting with periods of no noise at all to a series of audible slaps. I have heard other Caravans with similar sounds while shopping around pre-purchase.
All of them made the same sound, but not as loud as the Van I have now.
Is it possible that the timing chain on my particular van is looser or more stretched than others and this is why my slapping is louder? Would it be advisable to have it replaced or is this simply a quirk that although is not damaging or harmful to the motor, it remains an annoyance if you focus on it too intently?
Like master tech said, you need to isolate the noise. Get yourself a stethoscope or make your own (about 3/4" od hose with bolt stuffed in the end). Touch the bolt end to the engine and the other end in your ear. Pay special attention to the valve covers and oil pan. You may have a difficult time getting it near the timing chain.
I doubt it's a rod knock. Rod knocks are worse when oil pressure is low. When you first start your car does it knock? It takes a few seconds to build oil pressure. When the car is warm is it worse than cold? Does it do it more when the oil is old and worn out? Warm or worn out oil is thinner and lowers oil pressure.
Intermittent doesn't sound like a rod knock. They are pretty predicable.
Without hearing it I would guess a lifter.
2002 Dodge Grand Caravan Sport 3.8L AWD 146k
Driving a minivan is like riding a girls bike... It's disturbingly comfortable.