Why does the trooper's engine cut off after shifting into Reverse or Drive?

What is your question?

The car starts fine, New battery, no rattling after car has started ... But when it's shifted into Reverse it goes dead. A few friends tried to push it once it was in neutral & then I shifted to drive..and it went dead again. - A repair shop said a new mass air flow sensor may or may not fix the problem. I'm trying to save money & don't think an air flow sensor is the main issue here. Any ideas??