Fuel delivery/OBC question.... (archive)

I have been using the OBC to see the "novelty" of seeing my average mpg, it used to display around 14mpg, now its down to saying 7-8,mpg. But I drove about 300 miles to my brothers college, and I figured out I averaged about 14-16 mpg. So how does the OBC figure out the Average MPG? Also, I heard a noise back by the left rear wheel (where the filter is) that sounded as if it was clogged, but the filter was replaced about 9k miles ago, so what's happening to make the noise and make the OBC think I'm gettin 8mpg when I'm getting about 14-16mpg?

I guessed that the OBC figured out the average mpg by how hard/long the fuel pump is working, so if its clogged it would still get good mpg, but the OBC whould figure it wasnt becasue it was working so hard. Is that how it works or is it totaly different?

Any help would be good...Thanks,
~James

Follow Ups:

Re: Fuel delivery/OBC question.... Scottie 85_535i 84_745i San Jose CA 02:37 12/09/2001 (2)
- Can you adjust the clock timing with this too? James '82 733i 14:57 12/09/2001 (0)
- Scottie, how to remove cover? stevecots CHI 84/85 745 07:49 12/09/2001 (0)
Re: Fuel delivery/OBC question.... Rob Raine ('85 735i SE) 01:57 12/09/2001 (1)
- Hold down RESET, not CONSUM. Sorry... Rob Raine ('85 735i SE) 05:19 12/09/2001 (0)
Re: Fuel delivery/OBC question.... mike wong 21:14 12/08/2001 (0)

[ Follow Ups ] [ 7-series (E23) Message Board ] [ Msg. Board FAQ ]

Questions, comments, or problems, please visit the Roadfly help desk.