Vibration

[Orlando]

Hello there, can someone please tell me why my 2007 Envoy vibrates only when I turn the a/c on? Spark plugs and and air filter has been replaced. Also check engine light is on and the code says that it's the thermostat. Not sure if the thermostat can cause the vibration. But it will be replace in a few days. Thanks

[carriedi]

p0128 is pretty common if the engine takes too long to heat up. doesn't cause a vibration. if it's on;y when the ac is on I would look at the idle and compressor. the ac compressor put a pretty big load on the engine so the idle should bump up when the ac turns on. if the idle doesn't go higher when the ac is on the compressor will bring the idle down and that could make the engine vibrate. or it could be the compressor it self. it could be binding up causing the vibration. watch the drive belt watch the belt and tensioner and see if they are vibrating that matches the vibration