Can't keep my 99 GP running

3800 Grand prix GT. It stalls out, & usually won't start back up. When I do get it running I have to rev the engine to keep it going. & it seems to miss sometimes, but doesn't store any misfires in the computer. The exhaust is black & smells very rich in fuel. I scanned the computer with my MT2500, & there is no codes. I checked the MAss air flow, idle air control, & TPS sensor. Doesn't appear to be them. Could this be ignition coils? My O2 sensors appears to be in range.

I am lost. what ever it is, it came on suddenly, & nothing appear to be out of range to set a code.

Thanks, 68ragtop

turns out it only runs like this when it is warm. On cold start up it is fine, then gets progresively worse. Maybe its a temp sensor & the engine thinks its always cold?

try changing your spark plugs. that may help.