hmmmmm. I tried adding the tables as well and not results
$myTables = 'body_type,cylinders,drivetrain,engine_placement,engine_type,make,model,model_body,model_details,model_engine,model_name,model_performance,model_specs';
I have even tried adding the tables with the prefix.
Can you manually write your schema? They're generally quite straight-forward.
https://docs.modx.com/xpdo/2.x/getting-started/creating-a-model-with-xpdo/defining-a-schema/defining-the-database-and-tables
Once you've got your schema, just point that initial script I pasted at it and it should build it for you. Note that you need to manually create the database first. Just make sure it's UTF8 and empty.