I've been up and running on the Haltech since mid to late May and just recently within the last month or so have been running full E-85. The flex sensor and the Haltech work great together but just as of lately I've been having a bit of an intermittent issue and i've not changed anything to make this occur.

Sometimes, randomly after the car has sat for a few days I will start the car normally and notice the IDLE will be way off and the car will want to stall... After hooking up laptop the Flex sensor is showing 0.0.... After a reboot of the ECU and the car I can get the sensor to read correctly and the car will run and drive fine after that.

I have the GM Flex fuel sensor on the return fuel side in-between the secondary fuel line and my FPR mounted on the firewall. Any ideas to what could be occurring? I recently updated my ECU firmware to 2.45.02 and also my ESP software to the most recent available in hopes this could solve any software issues. My tuner is pointing at the possibility of an air bubble settling in the Sensor causing a false reading.

Thanks for the help!
-M

 

I’d power on the ECU, let the pump run through it’s prime cycle, and see what the sensor reads. If it’s stays at 0, key off/on to prime again and see what it does. If the line is bleeding off, you may need to up the prime time to get fuel to the sensor before starting the engine and have the patience to let it prime before attempting to start it.

 

Thanks, I will check the prime time in the settings. I typically wait for full gauge sweep (up to 7k and back to 1k) before cranking. I had to call Aeromotive concerning the fuel pressure regulator as after about 500 miles it would not longer hold prime longer than 2 or 3 seconds after turning the key back off. They said this is " normal " .. It holds pressure just fine while running and rises under boost as it should so I guess it's "Normal"

I'll up the prime time another second and see if that helps and also try mounting the sensor at a slight angle to allow any bubble to rise away from the sensor area in the center.


Thanks!
-M

 

I was able to resolve this by relocating my Flex sensor lower on the fire wall. It now sits just above the transmission area in between both the secondary fuel rail AND my fuel pressure regulator(FPR is mounted near the HVAC pipe bracket on the firewall)

Doing this should allow fuel to flood back into the low point where the sensor is located and allow composition to be measured at startup. It was previously the high point of the entire fuel system.

Thanks! M

 

I spoke too soon. Went to drive the car to work this AM and sure enough it started and ran like crap, I knew right away.. plugged in laptop and confirmed 0.0 fuel composition!

In its current location it should have fuel sitting in the sensor. After trying for 5 minutes of tapping the sensor and trying again it still read zero, I even tried increasing prime time to 6 seconds (up from 4) and no go. , so I gave up and drove the daily.

I will purchase another sensor and also check connection at ECU and keep trying !

 

Update ! I opened a number channel in Haltech to check hz on the flex sensor and it’s reading 0hz. So therefore she’s been flaking out and it’s not air bubbles ect.. like I thought. Should read 50hz minimum for 0%E. I replaced the sensor with the smaller version without fuel temp (I am not utilizing fuel temp at this time). The swap was quick thanks to the quick connect hoses. Back up to 120hz which is 70% E content. Woot. Now I wonder why the other failed within 4000 miles..

-M