Last days, RBK ( Rebe ), my old faithful Volkswagen Passat TDI show some signs of weakness. Symptoms: Suddenly loss of power. Car, very lasy! The car didn’t accelerate as it usually does and with the gas at full, yon need a century to go up at 100 – 110 km/h. ( 62 mph ) The engine go up to 2000 rpm then hold around there, and no further.
Ok, first think, maybe it was the gas filter or, god, hope not, the turbo is broke or jam.
But normally the turbo didn’t broke easily at this cars, and the filter was new, so let’s check the sensors chain. I wrote this small tutorial with images to teach step by step maf replace.
With vagcom and a cable it was easy to diagnosticate, but I have not those things. (Today i have! I made for my self a vag-com cable. )
So without proper equipment, let’s try step by step. Take some Spice from Dune and with the help of The Force i start with the MAF Sensor. His location as show in pictures, is just after the air filter. So I chose the easiest way to test your maf.
The very easy way to diagnosticate this sensor is to pull out the just the cables and test the car on the road. If the car run in the same way, or even better, you can be sure, the MAF sensor is gone. That’s exactly what I did and the car accelerate better without the MAF connected.
Hurray, is not the turbo! The MAF is broke.
The MAF, Mass Air Flow meter is the sensor who indicates to the ECU (car computer) the air mass who flow inside the engine.
I take it out, and try cleaning. Usually if is not completely burn out, a good cleaning with isopropylic alchool can do the job.
But not ever think to touch the sensor itself with something, like paper or a stick with cotton. Just alchool or clear, very pure contact spray for electronics.
Don’t spray directly on the sensor. The power of the spray jet can damage it. The best way is to immerse the sensor part in isopropilic alcohol and let it about 30min with gently shake from time to time. Please, DO NOT open the sensor, do the cleaning with the sensor as it is, unless you have nothing to lose and you are prepare for a new one!!
If this treatment do not restore the MAF sensor,
maybe is time to buy a new one. If you have BOSH, you can buy also a Pierburg one, is (at least here) much more cheaper and work great.
On my old BOSH MAF I do a autopsy and I put the pictures here and a repair tutorial. Remember this sensor is burn out, do not open yours.
The MAF sensor work by heating a small filament at a certain temperature. With the air blowing over, the temperature drops. So the filament need more electricity to rise up the temperature. The ECU measure the power needed to keep the temperature, and estimates the mass of the intake air.
MAF defects can show because the dust from the air, or more often from microscopic drops of oil, especially if you have sport air filter, with oil.So, the conclusion: if you have Volkswagen Passat TDI, or Skoda TDI, or anything TDI with MAF sensor, if your car lacks power is lasy, do not panic.
First, disconnect the MAF and test the car. If the car runs nor badly but the same or even better, then you know, is most probably the MAF.