Misfires when switching to the 4th gear?

Hello,

It is strange why the engine will only misfire going into 4th gear.
If there is a drivability issue going into 4th gear it is more likely an issue with the transmission rather than the engine or misfiring.
If there were misfires it will misfire while driving in any gear or under load (acceleration) or being in idle.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

It could have a shift issue like a transmission shuddering going into that gear. A transmission shudder can happened due to low or contaminated fluid in the transmission.

https://www.2carpros.com/articles/automatic-transmission-problems

It will be best to do a through inspection of the vehicle. Also use a diagnostics tool to scan for any engine or transmission trouble codes.

Do keep in mind when a vehicle has a transmission issue it could become expensive to fix. But it will depend on the exact issue.

Please let me know of any questions.
Thank you.