This is right from GM, As I am a GM Certified technican and have access to this info, thought I would pass it on to you and hope it works for your problem.
#PIT3116A: Engine Stalls When Air Conditioning Is Turned On At Idle - keywords HVAC rough condition CJ2 CJ3 surge - (Dec 15, 2006)
Subject: Engine Stalls When Air Conditioning Is Turned On at Idle
Models: 2004-2007 Buick Rainier
2002-2007 Chevrolet Trailblazer and Trailblazer EXT
2002-2007 GMC Envoy, Envoy XL and Envoy XUV
2002-2004 Oldsmobile Bravada
2005-2007 Saab 97x
This PI was updated to include models through 2007. Please discard PIT3116.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Engine may stall with the air-conditioner on and or while adding additional loads to the engine at idle. An example of an addition load would be turning the steering wheel left or right with the air-conditioning on. This type of stall usually occurs during idle or slow parking lot maneuvers. This concern may not set any diagnostic trouble codes.
Clean the throttle body bore and the throttle valve plate using a clean shop towel with GM top engine cleaner, GM P/N 1052626 (Canadian P/N 993026) or AC-Delco Carburetor Tune-Up Conditioner, P/N X66-P, or an equivalent product.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance
Sunday, April 6th, 2008 AT 10:44 AM