XFI Flex Fuel mode issue ...


Wondering if anyone else has ran into this. I recently installed my flex fuel sensor, when I enable flex fuel mode with the key on engine off it displays the new FEC .690. Seems to me the sensor is working and ecu is seeing a proper reading. I try to start the car up and I have to constantly feather the throttle to keep it running otherwise it will die. So I disable flex fuel thinking some how that's the issue. it shows the old FEC of .680 but is now doing the exact same thing having to feather throttle to keep it running, which never happened until I enabled flex fuel mode. Next I load my previous tune back into the box which does not have flex fuel enabled and the car fires right up and runs like a top. seems to me that somehow by enabling flex fuel mode I am corrupting my tune. Do I need to do an update or re flash the box ???
Sounds good I figured I would throw it out there and see if any one else has had a similar issue.
Ill just keep it disabled for now and try and sort it out.

Did you initially tune the car with E85 & not have the correct fuel energy constant? It shouldn't run correctly with E85 & a fuel energy constant of 1.00
It has been running on E85 the past year or so and i've been refining the tune FEC set at .680. I decided to finally wire in a flex fuel sensor and try and get that on board. Signal is going to A6, ground is going to batt. ground and and 12v ign is spliced into b17 on the ECU.
So I understand correctly, you have an FEC of 0.680 with the flexfuel box unchecked and it runs fine. You then check the box and the FEC changes to 0.690 & it runs lean?
If so, try hitting "Apply" a second time on the Fuel Calc Parameters table.
Also, be sure you have the FEC Spark table populated

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That's correct FEC set at .680 runs fine. I check flex fuel mode and hit apply and then start the car and need to keep feathering the throttle to keep it running. If I let off the wideband starts to read lean and the car dies. Then if I go back and un check flex fuel mode and hit apply it continues to run bad. I then load in my previous good tune without flex fuel on and it fires right up. Are you talking about the Spark offset vs. FEC. table? If so there is a curve that you had put in when I purchased the box. .680 is at zero correction and tapers down from there. I will try hitting apply a second time and see what happens tonight.

Thanks cal.
So apparently at some point while I was tuning the car I didn't hit apply after changing the FEC or turning off flex fuel mode, some how I tuned around that fact and had the car running well. After talking with cal I decided to start over with my base tune with flex fuel mode turned on and make a new flex fuel tune for the car this weekend. Thanks again cal !
Me too . Im not exactly sure when it happened but it makes sense now why it was not working properly. Flex mode is now working and Ive made a new tune.
Interesting to see what kind of fec numbers your getting from tht sensor live?
yea more or less just assurance of what the actual FEC is. I previously had the FEC set at .680 and tested my fuel to make sure I wasnt getting a bad batch. It tests out at 85% ethanol during the summer months pretty consistently here in MN and the sensor is reading .688 currently.