Van does not want to accelerate?

Hello,

It sounds like when the engine under load (acceleration) it misfires. That's why its sluggish and shakes.
Typically when an engine misfires it turn the check engine light on.
If the light is illuminated, getting it scanned would be a good first step. As that can help diagnose the issue.

https://youtu.be/vMwTzURWXmk

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Check the spark plugs for wear and make sure the gap is set correctly.
The factory recommended gap is 0.048 - 0.053 in.
If there is excess carbon build up on the plugs it is likely the reason for the misfire.

The spark plugs can be replaced using basic hand tools.

https://www.2carpros.com/articles/how-to-change-spark-plugs

Please let me know of any questions.

Thank you.