timing belt maybe?

[tom4bren]

The 'slapping noise' that I was getting in the Amigo was the serpentine belt. I had just replaced it & when I was setting the belt onto the tensioner I didn't notice that it slipped over a notch on the crank pulley. The crank pulley did a very nice job of slicing off one rib of the brand new belt & that sliced off section was slapping the snot out of the engine compartment. Luckily the only damage done was to a wire bundle (probably not common to the VX since I lost the 4WD, reverse lights, & shift indicator). Mebbe someday I'll actually get in there and fix those broken wires

Probably not your problem since it sounds like you've already inspected your serp belt ... just thought I'd share as a warning when you go to put your serp back on.

[MSHardeman]

One thing to check would be the timing belt tensioner. Others here have had a tapping sound when the engine was running and thought that it was something IN the engine only to find out that the timing belt tensioner was bad and was allowing the tensioner pulley to "flop" around causing the tapping. That could also throw your timing off a bit as the belt isn't as tight as it should be.

It's a fairly cheap and easy fix, but you do have to get a lot of stuff out of the way in order to get to the timing belt tensioner.