Wife's '93 Sunbird 3.1 L/auto, convertable, loaded, about 130,000 miles on it. Problem with warming the car up on these here cold Michigan mornings.

It starts just fine, but it don't seem to want to do a fast idle for very long, maybe 1100 RPM's for about 15 seconds, then it drops to 850 or so, normal idle in park type speed.

I'm thinking it's the coolant temp sensor, but not sure. Could be something in the idle control system. I'm not real up on all of this here electronic gizmo gadgetry that's on anything past say mid '80's vehicles. So,,, I'm at a loss here.

I know that it is reccommended that the sensors to be swapped every so many XX,000 miles of driving, maybe it's time for a new CTS. Where it be located on engine?? Anything else I should check, replace?

Thanks,

Tom R.