Maybe 3 times in about as many months I've had code 2BC0 pop up. "Mixture Control, Fuel-air mixture too lean." It happened again this past weekend, and I cleared it as everything seemed fine. Then while driving I noticed my live MPG display in the message window of the tachometer was unbelievably high, but not consistently so. It bounces around as a live read will, but occasionally reported 50mpg while doing 75 on flat ground or even up a slight incline, with nasty wind.

So, that code on its own can mean a lot of things. I ran a couple of fuel ups with injector cleaner, prior to this last error code display. I'm not convinced it is an injector problem. Any ideas what could cause both the 2BC0 and falsely high fuel economy? I have to believe they are inter-related.

As an aside, and maybe relevant, I do seem to have a crankcase pressure problem , maybe, that manifests as an oil leak. This leak is assumed to be at the front crankshaft seal despite replacing it several times now. Replaced pcv valve.valve cover assembly two weekends ago with no effect on leak. I'm kind of wondering if something could be wrong with my catalytic converter, as I believe that would lead to 2BC0, and believe would also cause crankcase pressure.

 

Bumping this with a primary question: Anyone know potential causes that make the live miles per gallon reading fluctuate WILDLY while driving? Think 15-67-32-25-97 kind of immediate fluctuations

Asking as may point a finger at specific sensors.

 

Road conditions, wind speed, traffic, etc.... If you can go out on a relatively calm day, on a flat stretch of highway, and set the cruise control, you might get a better idea of instantaneous fuel economy. More important would be tracking long-term fuel economy. Get a reading when you fill up the gas tank, and keep track of average. Comparing that over the long term will give you a better idea of any issues that might be popping up.

 

Thanks for the response njaremka. You're right of course if analyzing mpg is the goal. And to that point I'm usually low 20's average. However, in my case I'm thinking the rapid mpg fluctuation could be an indicator to other problems I am having. My apologies for not being clear, I don't mean to waste anyone's time.

At the time of the original post here, if I were to drive and look at the instantaneous mpg readout (not average), on a calm day, flat road, cruise control set @ 70, etc... the instant mpg reading occasionally fluctuated as wildly as previously stated, noting that the inst. mpg display updates every 2-3 seconds or so. To me that says the computer is reading WILD signals from the sensor inputs used to compute mpg. From that I hoped figuring out which sensors are used for mpg readings and might point the finger at particular sensors, which then may also sort other problems I have been having.

 

When I am trying to look at fuel efficiency on my 2012 R 60 justa, six speed manual, gasoline, I get on a flat stretch of road and do not use the cruise control. I hold the gas pedal in one position (wedging my foot against the carpet on one side to help hold that position steady) at constant speed and observe the instantaneous mileage. Using the cruise control, it just fluctuates too much to mean anything. YMMV

 

Thanks for chiming in Paul. I'm grateful. I would not have expected foot-brace cruise control to be more accurate and predictable than automated cruise control. Very interesting in and of itself.