[w3wlp]

I have a 2007 Aveo with 20,000 miles on it.
Suddenly it just started stalling when stopping for traffic lights or stop signs, or just in heavy traffic.
Engine restarts OK but idles at 750 rpm instead of 1,000 rpm, which it has been doing since it was new until this problem started. As long as I feed gas to keep the rpm above 750 rpm, it doesn't stall.
Now the "service engine" light comes on.
Unfortunately, I did not buy the repair manual (Helm Inc) - first time in fourteen GM vehicles. Can't find any info anywhere about this problem (Manuals are on order now).
The car has been in the garage for four days, after an initial visit last week when they said it was fixed... guess they were just buying time that day. It's under warranty and they said they've now got the parts based on a service bulletin... about injector seats or something in that area.
It looks more like a pollution control problem (in the past the engine light is fixed by reseating the gas cap!).
Anyone ever hear of this condition?
Thanks.
Norm