Mass Air Sensor

Oct 31, 2004 6 Replies
D

FYI, My MAF sensor was acting up last year on my 99.5 Jetta TDI and once I replaced it with a new sensor (a Pierburg), it made a heck of a difference. It would actually get up to speed like it was supposed to. The only problem is that about 10k miles later, the car is starting to show signs of the MAF sensor going bad (just like before). Last night the engine light came on. I'm sure it's the MAF sensor although I haven't checked the code(s) yet. Talk about frosting my @$# like a 3ft tall snowcone. Sorry everyone, I felt like I had to vent my frustrations. It's a great car except for the dang MAF sensor.



By the way, how about those diesel prices? $2.29/gal in OH. I'm just glad the car gets such good mileage.



Dave


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R

There should be a warranty on the MAF's now... We got money back from VW Canada for our MAF replacement costs, and the dealer said if it happens to break again, it's covered... I would hope VWoA would be the same.

Diesel prices are too high... 84.9c a litre, gas is fluctuating from the mid

70's to the lower 80's.... At the start of summer diesel was 69.9c a liter, and gas was closer to 90-1.00 per litre.... And it's getting colder out, so my fuel consumption is going up.
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T

Have you done anything about cleaning the sensor prior to replacement?

TBerk

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J

As I recall you'll need a microscope to see what makes them tic. There's a small foil strip that is heated up. Then air passing by it cools it off. The amount that it is cooled is what the computer is looking at. What happens, at least on the tdi's, is the foil gets contaminated with dirt, oil or whatever then burns out because it gets too hot. Somewhere at

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is a write up complete with pictures. MAF's were/are a big problem on 99.5 and onwards tdi's also. The pre 99.5 tdi's used a heated wire. The wire is more robust and the computer even has a "cleaning cycle, wher the wire is heated enough to clean it's self. However the wire ones are slower to react.

JoBo

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B

Not quite. It's a semi-conductor now; "hot-film" being either ceramic or silicon substrate over which the air passes cooling the resistive "element" formed by the semiconductor.

And the wire ones also didn't have means of compensating for pulsating flow (flow direction is discriminated by newer hot-film sensors) so that only inflow is "counted".

This is even more important in a diesel than gasoline engine because there's usually no throttle plate.

Contamination of hot-film sensors by oils is a problem for all manufacturers.

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