Northstar Engines and System Technical Discussion Discussion, '99 Seville STS in Cadillac Engine Technical Discussion; Engine stalls......not every time but about 50% of the time--after idling at lights, etc. And also---if moving very slow---like pulling ...
Read the sticky thread at the top of the page down in Cadillac technical Discussion, Technical Tips: How to pull codes on.........and later Seville/Deville. When you pull your first codes, write them down but don't clear them. Use the links to decipher each code and come back here.
(Just realized you been there, done that - sorry. not enough coffee yet..........)
If you get P0335/6, P0385/6, and maybe P0300 you have a CKP (CranKshaft Position sensor) fault. www.rockauto.com or www.gmotors.com, $110 in parts (get both sensors) and a couple of your hours on your back. Not fun, but do-able.
(Too bad Lexus wouldn't let Danica Patrick in the U.S. Open advertising mix - Ford wanted to have her in a "topless" Mustang and Lexus said "No".)