My question is, is 4.17V approximately 5 volts? I have tested the voltage at the map sensor, and the manual describes that both of the voltages should be about 5 volts. My results were 5.00 V pretty much on the dot, and 4.17 V. Is this "close enough" to 5V? As a little background info, my vehicle is a 1991 Honda civic std with an MPFI swap that I did myself (I took my time, did it right, and it started the first try with no real problems) Other than the swap, the setup is pretty much stock. That's right, stock pm6 fuel system in a d15b1, and I am aware of the fact that it runs a little bit rich. Not a huge problem if the car were to be kept in closed loop properly. Well, during the summer, shortly after I did the swap, everything was running beautifully; mileage was between 35-42mpg, which is what I'd grown to expect. I had a cheap air/fuel gauge, that I used STRICTLY to tell how quickly my o2 sensor heated up, and when I pushed the gas too hard, which obviously kicks it into open loop. As the temperatures began to drop, however, so did my economy. I went from about 41-42 mpg highway in the summer to under 25 mpg highway, as low as 18mpg normal driving. Watching the air/fuel gauge, the reason for this mileage drop is apparent: When it is cold outside, the car stays in open loop until a good 20 minutes after its been warmed up, and then kicks it into open loop again whenever the cars gets above a random speed, again depending upon the temperature. If it is a bit warmer, say 45 degrees, this speed will be as high as 60-70mph (3k-3.5k rpms). Colder, such as 15-20, and it will be as low as 40mph (2k rpms) Eventually, if I am on a long trip, after approximately 4-5 hrs the car will be functioning normally, keeping it in closed loop until I exceed 80mph (4k rpm) There are no CEL codes, never have been in quite some time (except when I unplug some wires during testing) I have tested the hell out of my oxygen sensor and tps systems, and they all perform flawlessly. I have also tried a different ecu, with the same results. So, could the map sensor be the issue (or the wiring to it?) Or does my car just have a severe gasoline addiction? Any advice would be greatly appreciated, as I have been trying to deal with this for several months now to no avail.