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Q: Idling rough while stopped on 2004 Cadillac DeVille

I recently filled up with gas, after almost running out, and the next day my check engine light came on. The car is idleing extremely rough, but runs well once the accelerator is hit. The computer diagnosis says that the gas is too lean. I ran the tank out and filled up again thinking it might be a batch of bad gas, but the problem is still occuring. You think it might be the Fuel Filter, Spark Plugs, Fuel Pump, or O2 Sensor? Thanks,
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In most cases a lean running engine is caused by a vacuum leak. On your 2004 Cadillac DeVille It is not uncommon for the rubber boot between the throttle body and the intake plenum to split causing a vacuum leak. Proper diagnose is critical in repairing a lean running engine. For more information regarding these lean fuel codes please look over this repairpal blog:
Common Problems:

* Vacuum Leaks (Intake Manifold Gaskets, vacuum hoses, PCV hoses etc.)
* Mass Airflow Sensor (MAF)
* Plugged Fuel Filter or weak Fuel Pump
* Plugged or dirty Fuel Injectors
I had the same problem and it was popping code saying two banks were running lean thought it was intake plenum gasket but never replaced because i noticed all my intake manifold bolts were loose i torqued them to spec 89 inch lbs and did them in sequence and light went off but still could be a vaccum leak somewhere cause if it is running lean then you are getting too much air
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