I have a 2000 Chevy Tahoe LS 2wd that at an idle in gear with the AC on, the idle varies from 400rpm-600rpm sometimes trying to die. What is causing this and how do I fix it. It has the automatic idle sensor.

My 2001 5.3 Tahoe does the same thing when the throttle body butterfly valve gets carbon up. It idles rough. You can spray some carb. cleaner in there, not a bunch. Important that you get the valve edges as clean as you can.I usually spray cleaner on a rag and wipe them off by pushing on the valve. It may hard to start at first and make sure you put the air intake back on before starting. Good luck.

It worked!!!!!!!