Well this just happened out of no where on me The car starts up and idles lower then normal. A strong smell of gas in the exhaust and there is a black coating around the bumper. Im getting around 5mpg and on a 30 mile trip one night i used a 1/4 tank. After the car warms up I get a stumble and SES light.
Something not related is if it rains a lot or is wet out for acouple hours my car wont start. Turns over then when i let off the key it stumbles. Im thinking thats a opti problem but would that make my car run really rich? I unplugged the MAF Sensor and that didnt help. Im thinking my O2 Sensors might be bad as well since I got headers last summer and I think those are the stock sensors. Maybe the headers burned them out. Any help or something I could try to figure this out would be great. Thanks!!!

 

o2s don't last forever. Might be your problem, given the symptoms. JMHO

 

So how would I test them??? Can I unplug them then the PCM will take over and use my MADZ28 Programming???

 

Check for shiny deposit on the shield or gummy crap, etc. Even if your main problem proves not to be the o2, replacing an aged on should provide better mileage.JMHO

 

Ebay has them for $30-$40 for OEM AC Delco which is way better than $80 from the dealer. I bought a set to put on after a few 100 miles as soon as the coating burns off the headers.

 

You mention you are getting an SES light, why don't you get the car scanned for the specific codes as that would most likely be a great help in troubleshooting your problem.