i would bet it is a resistor that you have to splice inline to trick the computer in some way. I would think about it if it were a plug in thing that you could take out when you have to go to the dealer or somthing but most of these i have seen you cannot take them back out without a lot of work.
Is it worth it? In two words, HELL NO!! They don't increase the fuel economy either, they decrease it. My brother got conned into one for his sebring and noticed a good 2mpg drop on his v6 He said he noticed slight increase in power but that's just because it made the computer think it was in cold weather so it just puts more fuel in, that's all it does.
It IS a resistor, placed on the air temperature sensor. The idea is that the ECU never "sees" the temperature of the incoming air, or it believes that the air is considerably colder that it really is. For compensation, the ECU adds more fuel to go along with the cooler, denser air to keep it's ideal air/fuel ratio. This makes the engine run a little more rich, which can add some torque down low, but overall doesn't do much of anything. Ford's ECU has an amazing amount of air/fuel maps which it references, and can even "learn" new ratio's based on feedback from the exhaust's O2 sensors. This gives a good chance that while the little resistor may work at first, the ECU will eventually reprogram itself to ignore (or self-correct) the input from the sensor, making your Ebay wunderchip useless.
[quote author=thereisnospoon link=topic=71097.msg1262051#msg1262051 date=1173666892]
Those things are trash. Someone I know bought one for their F150 and it was nothing more than a resistor inside a cheap plastic housing.
I'm assuming that you are talking about the ebay chip, not the K&N.
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