GMC Troubleshooting Questions? Ask a Mechanic for Answers
Hello I will help you with your question,
Minimum idle is controlled by the computer using the idle air control valve and is not adjustable. If it is high you have a vacuum leak.
Please let me know how I can help you with your question
You will need to see what the computer sees. With no adjustment available for minimun air then you know the computer is not getting the correct information.
Cleaning the intake tract, throttle body and checking EGR operation might get you some relief but the key is watching what the computer is using for input and judging if it's commanded outputs are being followed so that requires a good scantool and diagnostic equipment and time.
I hope you understand my answer to your question about the adjustment of minimum idle speed, there is no adjustment available.