I drive a 2010 Chevy Silverado with a 5.3 L engine and 3.08 6-speed automatic it has 123k miles on it.
I was just looking at what the computer spits out so I recorded it as I was driving back from picking up a bunch of landscaping bricks once I got back home I noticed that my fuel trim seemed a bit off. I then remember Scoty saying 0% is what you want. No codes but at 0mph before driving back my Long Term Fuel Trim Bank 1 was at almost -12%, and Bank 2 was at -9.4%. After driving Bank 1 was at -9.4% and Bank 2 was at -7%, could this be bad injectors or injectors that have been fouled up and could be corrected with fuel system/injector cleaner or do you think something more is going on?
I had a set of brand new spark plugs put in only 3k miles ago by a local mechanic and the work was double-checked by another mechanic at that shop
Links to the screen grabs from the drive (at the bottom of each image is where you can see where in the drive each grab is from)
https://ibb.co/GkrDRQW (0mph before)
https://ibb.co/k6m24TH (60mph)
https://ibb.co/34n70gq (45mph)
https://ibb.co/MscJ709 (10mph)
https://ibb.co/k6FM0R1 (0mph after drive)
what can you tell us about this?
Not much, all the gas stations here are 10% or less so im not sure how im getting that high of ethanol in my fuel, i would like to go with no ethanol but thats premium only and im not paying $4 a gallon when 87 (my what book recommends) is only $3.49
my truck is flex-fuel capable but there isnt an E85 station within my entire state and its a 6 hour drive to the closest one over 4 mountain passes ontop of that
my truck is flex-fuel capable but there isnt an E85 station within my entire state
that's what I thought
have a read here:
http://chevygmcvans.com/viewtopic.php?t=10911
I have to reset mine quite frequently
Should I go into my VCM Editor from HPTuners and turn off flex fuel entirely?
this is where I got the idea since I have access to tuner-tear equipment https://forum.hptuners.com/showthread.php?100808-Virtual-E85-fuel-relearn
The last time I used it I made it so my truck would not turn on AFM and cut me to 4 cylinders (it did this to me when I was climbing a mountain pass) and so I could update my tire size when I get new tires, and according to the forms at least it should force rest the system to 0% and I will never use E85 anyway.
Should I go into my VCM Editor from HPTuners and turn off flex fuel entirely?
if you have that ability, that could be a viable solution.
I've also heard of people modifying their trucks to take a physical sensor.
force rest the system to 0% and I will never use E85 anyway.
There is a caveat here as regular pump gas may contain up to 10%. Taking away the computers ability to adjust fuel flow rate means you may lose some horsepower.
so if i disable it, that would mean it might lock in on that ethanol content, if i could somehow tell the ECM all fuel will be using say 7.5% ethanol
i mostly use low grade which has 10% but every once in a while I use a middle grade which is a blend of the low and premium, so if I instruct the ECM to think all gas has 7.5% I should only see tiny amounts of lost horsepower correct? (or just start using only middle grade with that instrution)
In theory, yes. It's uncharted territory to me.
Are you really able to set any value you like?
Where I am, even premium gas has ethanol.
Where I'm at in the US people will not use gas stations that have ethanol in their premium (farmers use the same suppliers and would lose their minds), and I should be able to change it when I flash the ECM
If I can't change the content it thinks it at I, at the very least, can change the STOICH in the ECM since when disabled it will run like it is at 0% so if I shift the table over by 10% I would be able to make the ECM run like it always has 10% and; that little shift should let me run anything except E20+ and to be blunt I'm never going to.
well please let us know the results. I am curious.
But before doing that, you may want to try just resetting the alcohol content to make sure it fixes your rich mixture problem. If you're lucky it may even stay fixed for a while.
digging through the tuning software i can't change what it thinks the ethanol content is at (something to do with a safety lockout) so im just going to disable the flex system and shift the STOICH over 10%, im doing that tomorrow then I need to make a freeway run for a few miles so ill give you the update then or the day after
10% ethanol doesn't necessarily translate directly to 10% richer mixture. Ethanol is roughly 30% less energetic, so it could mean more like 10% of 30% which is 3%. You probably want to make small incremental changes while monitoring O2 data.
Again, I would start with the least intrusive changes first, and escalate as needed. ie. resetting the alcohol content
so the STOICH table is based on stoichiometry (dont ask most of it goes over my head, i only understand enough of it to know what the table does once the calculations are made)
the table is already doing all the work with the calculations (thank the lord) and its set up in 10% or 5% intervals depending on your vehicle (mine is 10%) so for a blanket 10% adjustment all i need to do it adjust the table over 10% and the fuel trim will be able to better handle the +-4% margin of error that is already in the table
so basically all i would be doing is telling the truck that; With flex disabled it needs to run at 0% STOICH, and I would have already shifted the STOICH by 10% so it can handle most gas, and I would just lose performance if I run premium but seeing how the 2010 5.3 only has a Compression ratio of 9.6:1 I would be wasting my money buying fuel that is pre-ignition resistant on a Compression ratio that doesnt cause pre-ignition on low-grade fuel
but I do agree im going to try the least intrusive first, tho im not sure if ill be able to get it to reset sense it uses virtual sensors and I really dont want to install yet another senor, even temporarily
im not sure if ill be able to get it to reset sense it uses virtual sensors
I have the "virtual" sensor, and I can reset it. All it's doing is resetting it's calculation which is based on refueling events.
If the option is there on the GM tool, I presume hptuners will have it as well. You should probably perform a fuel trim relearn after as well.
i hunted through all the menus and I can't do it on tuners, but I shut off flex fuel and flashed over the update and that did reset mine to 0 as a side effect, i also reset my fuel trim and started a new long term learning
You should probably perform a fuel trim relearn after as well.
I have that update for you, I did a light 31-mile (about 50km) freeway run at 80mph (128.7kph) with the STOICH shift and my long-term fuel trim is now at -.1% with a margin of error of -+.3% so it worked, my MPG on my dash has jumped by .4mpg. So in just 31 miles, the adjustments seem to have been very effective in both fixxing my fuel trim and getting me a little more MPG.
nice. I should find someone with flashing equipment who can disable it for me.
Hey, I have another update for you, I just did my first full tank sense the changes, and im up to 14.894mpg overall up from 13.048mpg, and I have been romping the gas
That's good news. And no noticeable loss of power?
Thanks.
Gained power acculy, im now able to keep up with my buddies racing truck, he still wins bc he has 400hp at the fly vs my 350hp but im able to hold my own now
