thanks a lot for your helps... I will save them for future reference for
myself and friends...

I am sorry for using the wrong term of *"vanagon syndrome"*... I should
know better and use something like *"problem similar to vanagon syndrome" *and
sorry for this late report.

so here's the update report...
since my son Nick is 1000+ miles away from me I can't help him myself and
all can do is relaying your suggestions and some of mine..

I suggested the following:

- disconnect the O2 sensor --> nope
- check the spark plug wires --> nope
- check the Hall sensor wiring --> nope
- check the Temp2 sensor wiring and connection --> nope

the last one is this: go under the bench, driver side, look at the
computer, disconnect the harness, make sure it's clean and reconnect it
tightly...

well.. bingo... the *"problem similar to vanagon syndrome" *is gone now for
500 miles and he's happy as a snail on a lettuce leaf...

aaah.. for some reason not clear to me and him the connector of the harness
was loose or iffy (to say the best)...

now I want to share a problem happened to me too... on my way to So. Cal,
500 miles from home, making a stop for gas and my 1990 tintop didn't fire..
it cranked OK but no start... check fuel pump, check Hall sensor, check
ignition switch, check computer harness, check spark plug wire, check Hall
sensor wiring --> all for nope, no start... then as a last effort before
calling for a tow, I unplug the connector going to a black box sitting on
top of the coil and replug it.... and guess what?  vrooom.. the engine
fired up right away....

again thanks you all...

dan