Volkswagen Repair: VW Passat hard to start after sitting for a couple of days., mass air flow sensor, throttle position sensor

Question
We have a 1999 Passat that has caused us problems that have resulted in tows in the past.  The problem is if it sits for more than a couple of days without being started in won't start.  It turns over but won't start.  A repair shop sort of fixed the problem in that they said if we hold the accelerator to the floor and keep turning it over it will start.  They said holding it to the floor shuts off the fuel injectors.  After about 10 seconds it starts.  The repair people can't figure out what causes the problem.  Do you have any idea what would cause this problem?  By the way, there are no "check engine" lights on and the car runs fine otherwise.  Thanks for any help you can give me.

Answer
Rick, thank you for your question.  This problem sounds like several things that could be at fault. One could be the Idle air control valve.  If it sticks it will not allow you to start.  You may also have a faulty air flow valve. Or possibly a Mass air flow sensor (MAF or MAP) is bad or faulty.  Also a possibility is the TPS or Throttle Position Sensor. Or even a “simple” vacuum leak. (to test for a vacuum leak, take a can of WD40 or carburetor cleaner and (using the included red tube with the can) spray along all vacuum lines and if the engine revs up, that is where the leak is).  Several of these things will not show up on a computer diagnostic of the car, especially the handhelds but MIGHT show up on a “SUN” or “BEAR” System.
Hope that helps