What would cause a car to run pig rich all of a sudden?
 

I have a 99 C5 with mods in sig, and had it tuned in the spring time and it ran great. I haven't done a thing to it, other than swap the Ti's for a Corsa system in August. I left in the beginning of september, and just got back yesterday. It's running SUPER rich, and when the car sits and idles (even after an hour of expressway driving) there is a cloud of unburnt fuel behind the car. What could cause this? It's always run too rich for my tastes, but not its not even driveable. The fumes burn my eyes and throat, and it STINKS!

I thought it might be an 02 sensor, they are the original ones and have 38K on them.

Sounds like an 02 sensor or if you got cats 1 could be bad or cloged. Goodluck :judge:

Hot car, and hot wheels! What are those, BBS LM's?

mine was rich due to a dirty maf

NICE, speedway white z06, beautiful!

Mine blew a piston! Did the same thing! Ran rich and smoked like a chimney! Do a compression test to be safe