Hey guys can use some 5.0 tech/help

[Suckerpunch]

About one week ago i picked up a 93 GT 5.0. with auto trans. The problem is when im in park the motor seems to want to stall. It will show the battery gauge drop off and start to die, but then it will catch its self and kick up the RPMs and smooth out again. It will keep doing this several times and ultimately die. Ive noticed it does the exact same thing while in drive when im sitting still by holding the brake (like at a stop light) but way worse. When I put it in neutral i can feel it just a little, but it never dies. While im driving it will shift up gears nice and tight, but when down shifting it seems to sputter a bit. Now just recently i have white smoke at high RPM.

any ideas?

Thanks,

Suckerpunch