I own a 1995 Honda Passport AKA: Isuzu Rodeo.

I have been driving it for two years with no real problems. The engine
has about 160K on it, and it ran fine.
There was always a slight tap in the engine, nothing that bothered me.
I kept the oil changed, and regular service. I was told it was no big
deal, just the tap of a poor engine. As long as I took care of it,
then it would be fine.

One day I went to get into the car after work, and I started it up.
All of the sudden there was this severe knock, or rattle. It sounded
like a mystical elf was inside banging on the engine with a hammer, in
time with the stroke of the engine . I figured, okay what now? I hit
the gas, and the tap sped up a bit, but not with the other little tap
I had. I revved it up to 2k rpm, and it disappeared. Now, I;m lost.
What the heck is the loud tap coming from?

I can't tell if it's coming from the left or right side of the V6. It
sounds like it's coming from the middle.

Can someone please give me an idea of what could be wrong?

Is there anything I can do to check it out?

I do brakes and oil changes. Anything besides that, maybe asking too
much.

If it is something serious, I have to get rid of it. If not then I
need to get it fixed.

Please help.