Hey, so I have been having some of these issues since the car was new so I dont know if they are related but now theres a new issue. I recently had a new starter installed because it stopped starting after being intermitant for a while. Now randomly when driving the security light will come on for a while and sometimes turn off shotly after, or othertimes it will just make the chiming noise like a warning light just came on but there wont be any lights. Also the engine light will sometimes come on. I coded it and I think it was an 040 number for bank one running lean. Many times when that comes on the car will loose power, sometimes when idleing, others when passing around 3,600rpm, and other times when having the cruise set. At first I thought it was a bad tank of gas but I have rean a couple tanks of premium through it and it hasnt changed much. Any thoughts?

Just one. Why would you run anything but premium in it?

Why would you, It has knock sensors and runs perfectly fine on plus. Talked to many GM mechanics and they said you dont need premium. I can still get 33mpg at 83mph on the highway and it has 263,000 miles.

I noticed in my buick if i use its keys while attaced to my key ring.with all my other keys(about 2 other cars and 5 buildings worth) the security light comes on.Also it sounds like you may have a bad 02 sensor.or possibly a MAF if you could get the code again it would help

Ill try to remember to scan it again tomorow. And I hate having alot of keys so I only have the one key and the remote. I was thinking o2 or maf but I would like to know which one rather than throwing a bunch of parts at it.

you can test the maf by unplugging it.The car will stumble and maybe stall at first but should cmooth out then take er for a spin and if the problem goes away then you MAF is bad.But scan it to see what codes you get..i just had an 02 sensor pull similar symptoms.just try not to really beat on her while its unplugged

The codes are PO440 - evaporative emission control, which I think is tied to the gas cap warring its had since new and the new one is PO171 - system lean, bank one.

on my 3800 the FPR and evap purge valve are tied to the TB at the same point with a rubber boot that cracks and if that was bad you could get both those codes. i dont know if the SC engine is the same.

P0171 is vacuum leaks or Maf. I've never seen this be an o2 sensor problem.
The emissions 440 is a bear to troubleshoot. Start with the gascap and filler neck.

When you say the car loses power, do you mean the engine stalls, or you just don't have the acceleration you normally have? If the engine is stalling I would suspect a bad crank shaft position sensor.