MPG gauge

[phucking-low]

I been fixing a neglected 91 bmw 318is over this winter. It had idle probelms, so i did the mess under the intake manifold mod/conversion and, replaced the rubber intake boot, and idle air control vlave. Next thing on my list is the MPG gauge on my gauge cluster, it seems to work but when its at idle its pegged at 0 on the gauge. If i rev it up to say 4k and let it idle down the gauge will move to 15-20 mpg and when it settles back to 1k rpm or normal idle the gauge scoots back to 0 mpg. I have not drove this car much just been in my garge so not sure if this is correct or not but i would assume that it should be pegged to the plus side 50 mpg instead of 0.

Something else the speedometer dosent work, not sure if it would effect the mpg gauge.

[flying_violin]

Mine stays at 0 mpg when idling, unless I'm cruising around in neutral. Then it's pegged over at 40+ mpg. Makes sense when you think about it: Idling consumes gallons, and if you're parked you are going zero miles. Never really noticed what it does during a 4k rev when stationary, though.