Car vibrates when in drive mode

Hi Jonathan and thanks for using 2CarPros.com. What you describe can be the result of a few things. First, when the aforementioned components are being used, there is a load on the engine that does not exist when they are off. The idle is controlled by the idle air control valve (IAC).

Here is a description of the IAC:
https://www.2carpros.com/articles/how-a-idle-air-control-valve-works

If you determine the IAC is bad, here are general directions for replacement:
https://www.2carpros.com/articles/how-to-replace-an-idle-speed-control-motor-iac

Here are general conditions which can cause an engine vibrations:
https://www.2carpros.com/articles/vibration-noise

I attached a picture of the idle specifications.

Next is the idle up solenoid. When the air conditioner is on, the IACV-FICD solenoid valve supplies additional air to adjust to the increased load. This could be an issue for your vehicle. I attached a picture if its location. Additionally, there is a flow chart for checking the idle up solenoid.

If the vehicle has been tuned, I am sure your mechanic has already checked for vacuum leaks. Just in case, here are directions for finding a vacuum leak. Ask your mechanic if this has already been done. If not, start with this first.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

If that checks good, my next step is the idle up solenoid. Follow the chart I attached below to determine if it is functioning properly.

I hope you find this helpful. If you have any additional questions, please feel free to ask.

Take care,
Joe