Virtual Flex fuel disable

[spina74]

I have a stock, untuned 2010 Escalade 6.2.
I've been battling an on and off issue with it running like shit, backfiring, dumping fuel etc. I was recently told about the virtual flex fuel issues with the alcohol content reading being off and causing issues similar to mine. My next option is to look at the flex fuel being the issue. Is there a way to completely disable it and if so, do I need to change any tables? I do not have e85 where I live and have no plan to run it. If a simple disable is my fix that's the route I'm going to take. The issue is on and off so telling when it will happen is impossible so it's difficult to scan.

Thank you.

[Cringer]

I have a stock, untuned 2010 Escalade 6.2.
I've been battling an on and off issue with it running like shit, backfiring, dumping fuel etc. I was recently told about the virtual flex fuel issues with the alcohol content reading being off and causing issues similar to mine. My next option is to look at the flex fuel being the issue. Is there a way to completely disable it and if so, do I need to change any tables? I do not have e85 where I live and have no plan to run it. If a simple disable is my fix that's the route I'm going to take. The issue is on and off so telling when it will happen is impossible so it's difficult to scan.

Thank you.

Yes just to to this field and set it to disabled: [ECM] 201 - Flex Fuel: Master enable/disable for Flex Fuel
Virtual flex is a virtual disaster and should never be used when doing any aftermarket changes to engine and/or tune setup.

[Alvin]

You should post a log of it acting up and let us diag it for you.

[spina74]

You should post a log of it acting up and let us diag it for you.

Unfortunately, I'm never near my laptop when it happens or it clears out by the time I make it home. I still have no intention of fixing the flex fuel system unless I do the sensor conversion.

[2xLS1]

Virtual FF problems typically aren't intermittent. If it computes the alcohol content wrong it is usually wrong until at least the next time fuel is added or even after then. It is usually the early Gen 4 FF trucks that have issues with virtual FF. I see it more on 07-09s and a few 10s. It seems like by 2011 they do it pretty accurately. I have a 2013 GMC Sierra 5.3L FF that is dead accurate computing alcohol content. You can just log commanded a/f in closed loop and see it it agrees with the fuel you are using.

[ponomar_pa]

Hello guys, is it option to disable switching it on/off?

[Tunercharged]

That is where you can disable it. I turned it off on my 2017 truck and some other vehicles I have worked on. It was fluctuating some and I didn’t see the point to keep it enabled since I only run 93 octane with the 10 percent ethanol that is widely available. Mine were virtual sensors anyhow.

[2xLS1]

I turned it off on my 2017 truck. Mine were virtual sensors anyhow.

Gen 5 trucks that have the FF switch set to Enable and the sensor set to Virtual are not Flex Fuel. Gen 5 trucks have to have a physical sensor for them to be flex. Gen 5 trucks that are not FF will all have Enable/Virtual.

[TGMachine]

I recommend disabling the flex fuel, especially in a virtual flex fuel application like this which does not have an actual fuel alcohol content sensor. I had issues in my 2010 Tahoe with the fuel alcohol content being off for whatever reason (never used E85 or anything other than regular pump gas) and I had to reset the fuel alcohol % with a Tech2. I have since disabled flex fuel completely and the issue has never returned.

[mikez71]

... It is usually the early Gen 4 FF trucks that have issues with virtual FF. I see it more on 07-09s and a few 10s. It seems like by 2011 they do it pretty accurately. I have a 2013 GMC Sierra 5.3L FF that is dead accurate computing alcohol content.

Great info, thanks!

I use e85 all the time. About a $70 fillup vs $125. Seems to work properly in my '12 Tahoe.

Was going to install a physical sensor, but if it ain't broke... (I'm only running a stock motor & tune.)