To fredfisher, I think you are the new record holder for miles on a 1998 C230. You can get your 250,000Km badge (20,000 miles ago).

To Michael,

Here is what I think I know: It has a thin platinum wire that has some electrical current running through it to heat it up. As air flows through it it is cooled. The resistance of platinum changes (slightly) with temperature. There is a control circuit that always tries to keep the resistance the same by putting more current through the wire to keep it heated up. In this way the computer can tell the exact mass of the air passing by by how much current is flowing into the wire. I believe that there is a seperate ambient temp sensor so it can correct for that. This system is improved over the old "spring loaded door" sensor that measured air flow but did not compensate for differences in air density. Anyway, for it to work it has to be kept clean, and I am told it does this by heating up red hot at every turn off, like a self cleaning oven sort of. I imagine that over time it erodes a bit and would lose accuracy as its surface area changes. Also some gunk could possibly build up. And they can even just break altogether. The engine uses the air measurement to decide how much fuel to add (by controlling the injector on time) and the O2 sensor(s) measure the results to fine tune the whole thing. Much better than a caburetor!!

Mike

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra