Hi. I purchased a 94 Isuzu Trooper in 2000. It had 76K on it and (aside
from the usual tapping noise) ran great. I got several years out of it
with nothing but routine maintenance, but last winter things started going
wrong left and right. I had to replace the radiator and the converter, the
clutch went, and it started burning oil. Something is rattling underneath
so I?m thinking a new exhaust is on the horizon. I?ve chalked these issues
up to the fact that it was a 10-year-old vehicle.

Unfortunately, at 140K it now has this infuriating starting problem. This
morning it turned over and then stalled immediately. After trying to start
it every 15-30 minutes I?ve finally given up and called out of work. Some
days it doesn?t start at all. It usually happens in the morning, but
sometimes it will start normally and then when I leave work at the end of
the day?nothing. Sometimes if I walk away for a few hours it will start on
its own, other times I need to be jumped. Whether it starts on its own or
is jumped the car makes this horrifying ?clunk? when it finally does turn
over.  

I can go for weeks with no problem and every time I bring it to the
mechanic they cannot get it to act up. I?ve replaced the battery and the
computer diagnostic says that the ignition system is fine. Any ideas? I
seem to have more trouble on rainy days. Could moisture be a factor?

Thanks! -Celia