[SpeedyCorky]

Car is a 2006 honda Insight, manual transmission (of course)

OK so the wheel speed sensor on the Insight is actually tapped in at the transmission, so i guess its more of a transmission speed sensor - but anyway...

So i got this sweet as MPGuino installed, and its a pretty simple little device, displays fuel consumption/mpg/speed etc. using the speed sensor, and the injector signal. calculate how long the injector is open (which is directly related to how much fuel is used), and related that to vehicle speed - and instantly calculate MPG numbers. Kinda like the stock Inisght FCD but better

So its all working great, EXCEPT that sometimes (often) the speed sensor is all over the map! i'll be going a steady 55mph (as displayed on the regular Insight gauges and again confrimed via stead RPM given by the Ultra Gauge), but the MPGuino displayed speed is jumping around: 52.04 mpg, then 56.5mph, etc etc. it jumps around a lot, but usually stays within about 5mph of what is the actual speed.

at higher speeds, and in lower gears (such as climbing a big hill at 50mph in 3rd gear), the reading is even more off. sometimes as much as 10 or 12mph above actual speed.

problem is that with inconsistent speed data, the MPGuino is unable to correctly calculate MPG!!! MPGuino reads i am going faster than i actually am, and hence spits out overly optomistic MPG numbers


why would the speed sensor be jumping around so much?
it seems to do it more in lower gears, possibly relating to RPM. but RPM is very low (less than 3000rpm) when i drive..
is this normal, and the stock speedo kinda 'averages' the imput from the speed sensor? (i doubt it)
maybe getting interference from another wire or system or something? i dunno


btw: the stock speedo on the insight does not jump around like this at all.