I've looked at several dozen threads about knocking, but none seem to address my issue, so here goes:
Specs: 2000 WJ Laredo, 4.0, 93K, selec-trak trans, oil changed about 2K ago.
Basic problem: Engine has begun knocking during low rev acceleration, both from standing and when shifting into second gear. Only happens when the engine is under load--not when at standstill. Does not appear to happen when shifting into higher gears or at highway speeds.
Interesting tidbit: Doesn't happen when gas tank is full, just when it gets below about a 3/4.
Sounds and feels a lot like dieseling, but doesn't continue to happen after engine is turned off.
This does NOT sound like the loud clacking in some of the videos posted, which some have suggested is piston slap, bad rod, etc. (Then again, I'm listening from inside the vehicle while moving.) More of a standard pinging/knocking you get in some cars with crap gas. (I usually use Shell or Exxon, so assume it's not a crap gas issue--though I did use No Name brand once in a pinch a few weeks ago.)
I can feel a slight drag on acceleration while this is happening, but that goes away once the revs increase and the knocking goes away.
Tried some fuel additive (injector and fuel system cleaner), but no help. Have not tried oil additive, as I have always felt that those are more likely to mask a problem than cure it.
Is this more likely (a) a GET THEE TO A MECHANIC NOW situation, or (b) more of an annoyance that is not urgent? Or????
Any thoughts welcome.