low miles per gallon

[RRoller123]

On the O2 sensor: Did you use a digital display, and how much did the readings jump around? When I do this at idle, it jumps .3x to .5x, an occasional .2x and .6x, and very rarely a .1x or .7x will flash. Looks like a bell distribution, around the .45 nominal. Do you folks find this to be normal?

[klweimer]

I used a digital volt meter and built a small harness with spade type quick disconnects to match the O2 sensor and the chassis harness. I brought a long lead into the cabin through the passenger wing vent and plugged it into the DVM (taking the other DVM lead to ground). I put the DVM on the dash and went for a drive. And yes, the reading jumps around a lot, especially once it warms up. When it's cold, it's pretty sluggish. The other advantage of driving is that it gets nice and hot, so when you stop and come back to idle, it gives good readings for a few seconds (20-30?) before it cools to the point of less believable numbers. All you can do is kind of estimate where it's spending it's time. I'm sure you could build some sort of averaging circuit to even it out, but that's not really my strong suite. I got this idea from the guy who wrote this article.
http://www.hiperformancestore.com/ljetronic.htm
Kirk

[RRoller123]

That makes sense. Good idea to view it while driving around. I did it after a drive, and with the engine doing multiple fan cycles at idle in the driveway. I bet an analog voltmeter would inherently do the averaging and the needle would effectively dampen itself, and roughly show the average. I have thought about doing an internet search for a small digital display that would display an average over a certain number of samples over time (100 points over a few seconds as an example), and display that, but I haven't done the search yet. That would be a pretty neat addition to the dash if it were discrete.

[Fiatlanta]

I got my 79 a couple weeks ago and have put a few tanks though in that time...got 18.6 on last tank using mid grade gas. Current tank is premium, so we will see.

So yeah...significantly less than the 25 mpg I've seen tossed around...