air flow sensor, oxygen sensors, catalytic converter and still the problem seems to be that somehow the gasoline is not properly being processed though the vehicle. Now, the car will start, and immediately die. Before it was very sporadic - didn't always die - then suddenly would begin to dog down, die, and then would restart. I've spent so much money on this car and still have the same problem. Any idea what it could be?
The car continues to have an on/off problem of dying. We've replaced the mass on 2001 Volkswagen Cabrio
by GL Dog Lover in Ketchum, OK on July 02, 2011
ANSWER by patrick mannion on July 02, 2011
I would put a fuel pressure gauge on the car and see if fuel pressure is present when the engine won't start, I would also verify that you have secondary ignition (spark at the spark plug wire). Check for fuel pressure (you will need a fuel pressure gauge and look up the specified fuel pressure for your vehicle). Remove the fuel hose that goes to the fuel rail and get a friend to crank over the engine to see you have adequate fuel volume (you should have approximately 1 pint of gasoline in ten seconds of cranking). Off course take proper precautions as gasoline is highly flamable. Next "listen" to the fuel injector. Using a mechanic's stethoscope (or use a long screw driver placing the handle end up to your ear place the metal tip end of the screwdriver against the body of the fuel injector), get a friend to crank over the engine while you "listen" to the fuel injector listen to each injector at the same point of the injector body. You should hear "click, click, click" as the injector is electrically opened and closed by the computer. If the injector is not being triggered you will not have fuel getting into the engine's cylinders. Disconnect the electrical connector at the fuel injector with the ignition key in the "on" position, (next position after the accessory position) you should have 12 volts at one of the two wires at the injector. This true for most vehicles but you need to consult a workshop manual for your vehicle to see that this is true for your vehicle. When the engine is running the second wire at the injector gets (triggered) grounded by the computer in your vehicle many times a second controlling exactly when and how much fuel gets injected into the engine.