After starting my 2004 Chevy Trailblazer, the engine will vibrate in Park and Neutral. When I shift from Park to Reverse the vibration increases. Shifting from Neutral to Drive is less intense than in Reverse. Turning on the A/C greatly increases the intensity of the vibration. When the A/C compressor turns on, the vibration increases, when the compressor turns off the vibration decreases. I’ve had a mechanic test the engine and transmission mounts for wear and damage. Mounts are good. Any advice would be helpful. Thank you, Ed Ransom.

First thing in morning when I start my SUV the RPM’s are about 900-1000 RPM. If I start driving immediately, the shifting is good and quick with slight engine vibration. If I wait until the engine idles down to about 625 RPM, there’s a delay (not slipping) in shifting and engine vibration. When I’m in Park and I’m listening to and feeling the idle, there’s a slight dipping sound and feeling in the idle then it returns to a smooth idle. Turning on the A/C the shift delay is longer and the engine vibration increases. Thank you, Ed Ransom