Volkswagen Repair: 2002 gti wont start, coolant temperature sensor, mass flow sensor

Question
Hello Rocky, I was wondering if you could shed some light on a situation with my gti. It all started when my MIL indicator lamp came on. When I ran the code, I got a reading of "too rich" or "too lean". I then researched this online I found that the air mass flow sensor my be faulty. Before I could change out the sensor my car just all of a sudden would not start. It seems that the problem would be the sensor but I am not sure. The timing belt is good and my spark plugs are "wet". Does this sound like the solution or have you heard of this before and there is a different solution? Any help would be great. Justin

Answer
Volkswagens have a provision whereby the fuel pump starts and runs for a little while as soon as the drivers door is opened.  The car anticipates being run, and charges the system with fuel.  If the key is on, and the door is opened, and closed a number of times in succession, the engine can become "flooded," and won't start.  It's possible to allow the car to sit quietly for a while and evaporate the fuel out of the cylinders, induction system, and turbocharger, etc. since the plugs were wet, I would open up the rubber tubing to the throttle body, and let everything get good, and dry first, then try to restart the car.  The too rich/too lean code could also be caused by the EVAP system as well.  If the vapours from the fuel tank are allowed to enter the induction system in too great a quantity, that will cause a too rich condition, and vice versa.  Furthermore, since this is a turbocharged engine the fuel "mapping" will be richer than a Naturally Aspirated engine.  Without access to a VAS 5051B, or VAS 5052 scan tool with the ability to read out fuel trim numbers at all times while you are driving, the repair could be a very subtle, hidden, difficult to diagnose one.  I would also add that it is possible to have a faulty engine coolant temperature sensor, and that will make the fuel trim too rich, or too lean, depending on what the "ECT" happens to be doing at that instant.  So, be careful.  You could be spending a lot of money to chase something that is cheap, and obscure.  Good luck Justin.  I hope this helps.