[PeteA216]

Sounds almost like the computer might need to be replaced. I had similar symptoms back with my Grand Prix, it threw me some codes too such as the idle air solenoid. After replacing some sensors and solenoids, nothign changed. Brought it to a shop, they said the computer was shot. Replaced that with a junkyard one, just swapped the prom. That was about 3 years ago and the thing's still going strong.