Hello, I have been driving my 1998 STS for 3 years now and have been having an issue with stalls for the last 18 months. When I pull up to stop lights occasionally the engine will stall out. This generally happens in cold weather most often. Generally if it stalls once on a drive it will then stall at nearly every stop unless I give it some gas. When it stalls, the battery and oil lights come on.
Edit: A few other symptoms that I had neglected to mention:
Car stutters a little right before it stalls. Drops from around 1000 RPMs to 500 then back up and then stalls.
Car has only stalled once in last 4 months after not running for 10 days. This is what convinced me it had something to do with weather, as once temperatures where consistently above 50 degrees F the problem seemed to disappear.
Car never stutters or stalls if the accelerator is even barely pressed
I have replaced the battery and was informed it may be an alternator issue. Any help would be greatly appreciated.