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I have a question about how my car uses the MAP sensor and O2 sensor. I have a '92 Civic LX. It has the D15B7 and an auto.

On my F150, the ECU uses the O2 sensor under certain conditions, but on the highway, it switches solely to the MAP sensor and a look-up table.

I have been reading about the Hydroxy systems lately, and looking for a bit more gas mileage, it seems to be an inexpensive experiment at worst. At best, it will save me some dough on gas. (The car is itself already saving me a bunch since I am able to park my F150 most of the time.) Anyway, from what I have read, people have mixed opinions about these systems, and that's fine with me. Flame away if you want, but I'm going to test it out and decide from the results I get. One of the things that has to be overcome is the computer's desire to keep the a/f mixture right. Adding extra 'un-accounted-for' fuel in the form of the extra gas tends to make the engine run rich because of the elevated levels of oxygen in the exhaust, or the fixed level of fuel being dumped in due to the MAP. So, the engine must be told that it's rich, so that it will lean out the mixture a bit. The two ways of doing this are to reduce the MAP signal and to bias the O2 sensor voltage. That all makes sense to me.

But I'm not sure if the Civic uses one sensor all the time, and the other part of the time, or if it uses both sensors all the time, or if it uses one now and the other later, or what. Can anybody tell me how Honda chose to use these sensors?

Dave

 
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I hate to be useless, but I'm in for results. You've made me curious, I don't know the answer.