Mass Air Flow Sensor
 

Sometimes the car starts - always when the open door light is on.
Sometimes the car wont start - always then the open door light is off - even though the door is open. Autoshop teacher say's it's a bad Mass Air Flow Sensor. - Any ideas ? Many thanks!

y should that have anything to do...

If you had a bad MAF you would have a code. Check that first then if it does it all the time. Leave the car on and while it's on remove the MAF sensor and see what it does. Usually if the MAF sensor is bad, REMOVING the plug will not make a difference on how the engine is running.