Scott, I live in Connecticut. I have an 09 Chevy Trailblazer LT3 I’ve had since it was new. It’s been well taken care of and never abused. In early spring I developed a rough idle (engine cold and in “drive” only) when I stop. Once the weather got warm and summer arrived, it went away. Now with the cooler outside temps returning, it’s doing it again. It’s got 200,600 miles. Again, ran perfect all summer and I only get this hesitation when the engine is cold and I’m stopped at a light. I’ve had throttle body and mass air flow sensor cleaned. The intake gasket was also replaced.
check for vacuum leaks
You need to have a scan run to narrow down what the problem is. It sounds like one or more sensors is failing and needs replacement, probably fuel related.
