Transmission Control Unit. Location ??? e34 1990

[Bellicose Right Winger]

Yes it does make sense. When coasting with engine speed over ~1700 RPM and throttle closed, DME shuts off all fuel to engine. Instantaneous MPG goes to infinity, full left on MPG gage, because you're accumulating miles but not using any fuel. When vehicle slows and engine speed falls below ~1700, DME turns fuel back on and MPG gage swings right to show fuel consumption rate.

In my 535ia I don't feel the effect you notice as you coast thru 15MPH w/closed throttle...although I'm sure my MPG gage behaves as yours does. Not sure if this is your trans downshifting, or some effect of turning fuel back on as I described above.

Paul Shovestul

Thanks Bill,

That answers one question but leaves another! The reason I am asking is that this:

My 535A has a strange driving issue when slowing down. Say you are doing 30mph light throttle and you take your foot off the pedal. The MPG guage slowly climbs to the right (0)mpg end and hovers about the 10-0 mark until you come to a stop. If you are doing say 50-60mph and do the same thing the guage swings to the (50)mpg end and past it (more or less fully left) and then once you get to 15mph you "feel" a gear change and the guage comes back from the left to about 30mpg and then with road speed drops to (0) (fully left) If you are in 'S' mode (sports in EU land and not snow) it can be made to do it on demand. The overrun feels like over run with the guage fully left and the car using some engine breaking once you hit the magic 15mph it feels like a gear or clutch engauges and the MPG guage behaves as if you were labouring a manual car.

Any of that make sence????!!!!!

Thanks

Steve

Oh I trust the unit is in the same (left hand side) on RHD and LHD cars?

[Steve_M535iA]

Sounds right, just did a quick drive and its at 1700rpm, so from what you've said that seems to be the reason. I guess it just one of those things you notice and assume the worsrt!

Thanks

Steve