how to solve? 1999 dodge durango 5.9L dies while idling?

1999 dodge durango was dying when i was slowing down at a light or going around the
corner intermitantly, and since we have had problems with battery cables coming loose
before we had them changed out, but still the problem persisted, i then had the system
checked for error codes and got 2:  idle air control valve, and the output speed sensor,
had these both replaced, as well as cleaning the throttle body. now it doesn't die as
often, but when i am stopped at a light and engine has been idling for a minute or two it
will still die, but always starts right up. also one time I noticed the gas gauge suddenly
stopped working, but within about 5 minutes it was working again. based on all these
symptoms, and the prior answers I read, this leads me to believe that there may be a
voltage leak, or spike?. what steps should i have a mechanic take to determine if this
is or is not the problem, any other suggestions if this turns out not to be the problem?

note: the mechanic i normally take this vehicle to has not been able to figure this out
yet (since he only spends a small amount of time with it between other vehicle work
and so far has only charged me for the actual work in replacing the sensors)
Kathy