GMC Repair: fumes?, fuel leaks, exhast

Question
Hi Marvin
My daughter has a 200 Cavalier that seems to be a good solid car. Lately there is a problem I cant figure. Upon starting the vehicle there is an exhaust and or fuel odor. This goes away soon. I cant find any fuel leaks, and the exhast seems OK.
Its most noticeable whe the car is started after not being driven for a while-as if there is more buildup to burn of or whatever. Do you have any idea what this is? Could it be a catalytic converter or something? Thanks for your thoughts!

Answer
I had a Corsica that had that problem as well. It is the O-ring on one of the fuel injectors. You can get O-ring replacements at your local auto store. If you can, have the codes scanned. It could also be the EGR valve. Those I do know, when you replace, is about $300. I bypassed mine with a jump I bought off of Ebay.