If you are not familiar with the location of the powertrain control module (computer), it is in the passenger wheel well area in front of the wheel. When you find it, you need to first get a good look at the connector before touching it so you know how it is positioned. Then see if it is tight. Also get a good look at the computer itself, especially the seam around it. These were a problem for water intrusion and especially problematic in the "road salt regions".
GM offers a protector that should be installed for future problems ( I'll send you the list of cars that qualify). The bad part is, they don't cover the computer. I don't know that this is your particular problem, but I v'e seen this happen on others like yours.
There is one other suggestion that may help. The intake valves can get a carbon build up, doing a variety of mis-deeds. If there is a significant build up, it can impede air flow and reduce effiecient fuel burning. I "think" the various air intake sensors adjust for the air flow, but the fuel problem is different. The build up on the valves:
and on the piston head will get dry from the heat of combustion. When this carbon dries it will act like a sponge, sucking the fuel into it as it enters the combustion chamber. Anyways, try this as good maintenance:
Try what I call an air induction service.
I like to use castle hydroblast. You spray it into a vacuum line such as the brake booster line if nothing else is accessible. Full spray for 3 minutes, stall the engine with it or have someone kill it while your spraying. Let it set for a few hours then take for a short drive in low gear, revving the rpms to help break it up. First use Castle cleansrite to clean the throttle bore. Try to get the throttle plates scrubbed good with a brush, while your spraying. Use a rag to wipe the carbon out between brushings. Seafoam is another good product, but smokes a lot.
IF you can't find Castle, here is my rep's email:
Wednesday, January 17th, 2007 AT 12:44 AM