When the heat is on, or the a/c, blowing a lot of air, it'll stall out...turn off at light or sign. What is the cause

Possible,vacume leak issue,have the vacume tested,if you have no engine light on.

The eNine light has been on

If engine light is on,go have it scanned,but IMO,it sound,s like the throttle position sensor may be bad,causing it not to idle under load.

Is that typically expensive and a lot of work?

Not really that bad,TPS is probably 70 dollar,s and labor 30 minutes,but that said go have it scanned to be sure this is the issue.

Thank u

You are welcome.

Try cleaning the throttle body and throttle body plate.

Go with nolene. This was my cause it would die when I turned on air and stopped at a light. Clean throttle body and drive on highway for 30 mins doing at least fifty it the speed limit indicated. But clean the body thoroughly before reassembley. The throttle body is the big black box on top of the car in the middle (mine says vortec) it has a big six inch around hose on it. Can't miss it. Hope this helps some one else as it helped me on a different forum

Yup me and my buddy got fixed thanks to T_S_T comment he has a Trail Blazer I got 02 Envoy basically the same vehicle one being GMC one Chevy but yes the lose of power at light or when turn on air and rough idle too but replacing the Throttle Position Sensor did the trick also cleaned the throttle body but now has Power in both vehicles Thanks TST :)