Will continually idle high in gear

Hello,

This could be due to a faulty idle air control valve (IAC).
The IAC controls the engine speed during idle by letting in specific amount of air. Over time the valve can become weak or get dirty and become stuck open or allow more air thru. That will make the engine idle higher.

The IAC can be serviced by cleaning it. Many times, which will improve the idle quality.

Take a look at this helpful guide:

https://www.2carpros.com/articles/engine-idles-too-high

I have attached diagrams for your reference.

Please let me know if you have any questions.
Thank you.