How to 'Entity Reference' using Rules
I believe I've resolved this issue; least it looks good so far.  Super thanks to Alauddin's response to "how to create rules to send email notification for node reference content?"

EVENT 
After saving new content of Car Review

CONDITION


Entity has field
data selector: node:field-car-review-node-reference
value: field_car_model_tag


ACTION


Fetch Entity by ID, with value: node and data selector: node:field-car-review-node-reference:nid
Set a data value, with selected data (that I want to change): node:field-car-review-node-reference:field-car-model-tag


I think I have this right, here is an export of my Rule:

{ "rules_term_ref_4" : {
"LABEL" : "TERM REF 4",
"PLUGIN" : "reaction rule",
"OWNER" : "rules",
"REQUIRES" : [ "rules" ],
"ON" : {
  "node_insert--car_review" : { "bundle" : "car_review" },
  "node_update--car_review" : { "bundle" : "car_review" }
},
"IF" : [
  { "entity_has_field" : {
      "entity" : [ "node:field-car-review-node-reference" ],
      "field" : "field_car_model_tag"
    }
  }
],
"DO" : [
  { "entity_fetch" : {
      "USING" : { "type" : "node", "id" : [ "node:field-car-review-node-reference:nid" ] },
      "PROVIDE" : { "entity_fetched" : { "entity_fetched" : "Fetched entity" } }
    }
  },
  { "data_set" : {
      "data" : [ "node:field-car-review-tag" ],
      "value" : [ "node:field-car-review-node-reference:field-car-model-tag" ]
    }
  }
]
}
}