Hondata

Hello Everyone,

Have been chasing an issue with my build that would cause it to start leaning out. I realized a few days ago that my ethanol content reading had dropped about 30% from the usual reading. If I turn the car off and on again the reading returns to normal but drops again after some time.

I’ve already verified that I have 12v at the flex fuel sensor plug and the output is securely connected to my Kpro. I’ve also changed the sensor to a brand new spare that a friend had but the issue remains.

Has anyone had any experiences similar to this? Would this be a wiring issue or possibly Kpro related?

There could be air in the fuel line that is changing the reading. Do you have a datalog showing the percentage changing?

I don’t currently have a datalog showing the drop, I could do that later on today.

When you say air in the lines, do you mean from lack of fuel pressure? Fuel pressure still looks to be fine. Car was running on a smaller pump a few months ago with no issues.

The pump could be cavitating

Did a datalog while driving and two while idling.

I realized that the ethanol content drops when my fans turn on or when any of my accessories are on as well (Dual nitrous bottle heaters, purge, probably fuel pump as well). I can also see the content dropped when getting off the throttle while driving.

The Flex fuel sensor is currently powered by a fuse tap in the interior fuse panel that I only tested when the car wasn't up to temp. I believe I may have to move its power source.

Spunkster wrote: Mon Jun 09, 2025 1:14 pm The pump could be cavitating

Any ideas based on these screenshots? If you suggest the pump I'll take it out and take a look at it again.

If the ethanol reading changes with electrical load differences that should be your first investigation. Also the sensor should be on the fuel return line not the feed.

Hondata wrote: Wed Jun 11, 2025 6:00 am If the ethanol reading changes with electrical load differences that should be your first investigation. Also the sensor should be on the fuel return line not the feed.

That was the first item I checked. I have good voltage to the sensor plug. Sensor is also after the FPR on the return line.

So, I went with the idea that it was an electrical issue.

Went through the major grounding points for the car and found that my battery ground had rusted over. Fixed it and made sure no rust would form over it again.

% ethanol content would remain within 1-2% of the original value. However, this morning while the car was warming up I realized it started running terribly. Ethanol content had dropped again but a quick restart had it running great again with the value in the correct range.

I’m running out of ideas at this point. Any feedback would be appreciated.