2001 Jetta Mass Air Flow Sensor Problems

If your 2001 Jetta is hard to start, idles rough, hesitates and stalls, your mass airflow sensor is probably the problem. If your 2001 Jetta has mass airflow sensor problems, your powertrain records a P0100 to P0104 fault code. A service technician attaches a scanner to the wiring system of your powertrain to read the diagnostic codes. The mass airflow sensor may need cleaning to restore normal operation of your fuel injection system.

Fuel Injection Cleaning

  • The mass airflow sensor is located inside the air filter housing or between the air filter and the multiport fuel injection throttle body. The mass airflow sensor measures the volume of air entering the running engine. The powertrain control module uses input from the mass airflow sensor to vary the amount of fuel into the engine. Cheap gasoline with less detergent or cheaper additives may have contributed to the problem. Additives form deposits in the combustion chambers. Liquid fuel injector plus intake valve cleaner poured into the gas tank when you refill the tank might solve the problem. Liquid fuel injector cleaner removes moisture from the gasoline, and cleans deposits from fuel additives off the throttle body and air flow sensor. An aerosol electronics cleaner recommended by the dealer or auto parts store may clean the mass air sensor. Spray the mass airflow sensor element, and let it soak for 10 minutes. Repeat.

Diagnosis

  • The mass airflow sensor generates 0.4 to 0.8 volts of current when your Jetta idles and increases to 4.5 to 5.0 volts when the throttle is wide open. A dirty or faulty MAF sensor lights "Check Engine" and causes a lean gasoline mixture in the throttle body. If the MAF sensor is filthy, too little air goes into the engine. If the load values do not change when the car is running, the mass air pressure sensor is probably wrong. Attaching a digital volt meter to MAF sensor values will also work. Normal sensor values show a smooth transition from idling to running. Jumps, skips, incessant noise or values that do not change indicate that the MAF sensor needs to be replaced. If the MAF sensor does not signal, the injector timing will be four times slower than normal.

Professional Cleaning

  • Deposits in the combustion chamber raise the engine's compression as well as its octane requirements. Cleaning the fuel injectors, throttle body, intake valves, tracks and combustion chambers in the car is recommended. Cleaning fuel injectors is a dangerous task because both the cleaner and the gasoline are highly flammable. Eye protection and skin covering is necessary. Pressurized fuel lines are disconnected and checked for leaks. Fuel injection systems are then cleaned by running cleaner through the running engine. As of December 2010, service stations charged $25 to $35 to clean each fuel injector individually outside of the engine.

Replace Mass Air Flow Sensor

  • Strong solvent may damage rubber and plastic parts of the fuel pump, fuel regulator and fuel lines. A cheap air filter contributes to mass air flow problems. Volkswagen air filters are best for your 2001 Jetta. Before replacing the mass airflow sensor, use a digital volt meter to determine the effect on the MAF sensor. The sensor is powered by a relay, and a second relay cleans the sensors and fuels the injectors. If the MAF sensor's output does not change or is erratic, the sensor needs to be replaced. Another alternative is attaching an oscilloscope to one injector as a terminal and another as a ground. The oscilloscope should show a gradually changing curve.