I am stumped and running out of money. My 1990 lumina 3.1L only
runs properly if hooked to a diagnostic computer or with the
alternator unhooked. Of course the computer is showing nothing wrong
but as soon as you disconnect it the car dies. It starts everytime but
won't idle or stay running under any condition. Ether in the intake
makes no difference. Everything has been replaced in the fuel system.
New fuel pump, fuel filter, fuel injectors, even a new computer and
battery. However I don't feel any of those things is the problem since
by simply unhooking the alternator it will run perfectly as long as
the battery has life left or pluging in the computer has the same
effect.
can someone help me please?

mushroomwick (AT) hotmail (DOT) com wrote:
What was the problem that started you on this trek to replace all these
parts? If it's been doing the same thing all along and you've replaced
everything you mention, why didn't you get a new alternator beforehand?
It seems as if you may have already isolated the problem, which
sounds like a grounded alternator....