Ethanol percentage flex fuel

[wsteele]

Just wanted to update.

Installed new upstream O2 sensors on the Burb and reset the Ethanol percentage with the Tech2. Drove down an topped off with 89 octane advertised as (10% E).

Immediately got on the interstate and set the CC at 75 and drove 40+ miles.

During this time the E % bounced all over, from 3% up to 18.5% and finally settled at 3.1% and staying there for the remainder of the trip.

Next day I checked the E % and it was back up to 13.7%.

At this point I think the truck recalculates the E % after every cold start or something... I don't know what the heck is going on with it.

I have seen the exact same thing with the percentage being a different number the next day than the last one displayed when I shut it down after getting home with a refill.

On mine though, it never recalculates again until I refill. It definitely doesn't recalculate every cold start.

 

[swathdiver]

I have seen the exact same thing with the percentage being a different number the next day than the last one displayed when I shut it down after getting home with a refill.

On mine though, it never recalculates again until I refill. It definitely doesn't recalculate every cold start.

Same here, it's got to be normal after watching it do this for four years. It was 62% a few days ago and 73% yesterday and hasn't been refueled in almost a month.

 

[wsteele]

Same here, it's got to be normal after watching it do this for four years. It was 62% a few days ago and 73% yesterday and hasn't been refueled in almost a month.

Mine never changes after it finally decides, the next cold start after a refill and drive round the day before. It might say 9% when I shut it down at the end of the day I filled it, then the next morning show 17% after startup. But after that, it stays solid at that number until I fill it again.

I think maybe the "virtual sensor" just doesn't do a very good job at getting the percentage really close.

I am still going to keep experimenting and also see if I can figure out why my evap monitor never completes and if that has anything to do with the "virtual sensors" inability to calculate my ethanol percentage more accurately. I did change the canister purge valve a few years ago and I think maybe it wasn't a genuine OE part, so maybe it is off just enough to keep the monitor from completing, screw with the ethanol calc, but not bad enough to throw a code. Just guessing here.

 

[kbuskill]

Mine never changes after it finally decides, the next cold start after a refill and drive round the day before. It might say 9% when I shut it down at the end of the day I filled it, then the next morning show 17% after startup. But after that, it stays solid at that number until I fill it again.

I think maybe the "virtual sensor" just doesn't do a very good job at getting the percentage really close.

I am still going to keep experimenting and also see if I can figure out why my evap monitor never completes and if that has anything to do with the "virtual sensors" inability to calculate my ethanol percentage more accurately. I did change the canister purge valve a few years ago and I think maybe it wasn't a genuine OE part, so maybe it is off just enough to keep the monitor from completing, screw with the ethanol calc, but not bad enough to throw a code. Just guessing here.

Mine wasn't completing the EVAP monitor test either.

I kept having a intermittent P0455 gross leak. I replaced the purge solenoid because it wasn't sealing all the way when commanded to by the Tech2 as it had charcoal pellets, from when I changed the canister, stuck in it.

The gross leak then became a small leak, I just replaced the fuel cap the other day and so far no codes and my EVAP monitor shows complete.

 

[wsteele]

Mine wasn't completing the EVAP monitor test either.

I kept having a intermittent P0455 gross leak. I replaced the purge solenoid because it wasn't sealing all the way when commanded to by the Tech2 as it had charcoal pellets, from when I changed the canister, stuck in it.

The gross leak then became a small leak, I just replaced the fuel cap the other day and so far no codes and my EVAP monitor shows complete.

If your evap monitor is completing and you still are getting haywire ethanol calculations, I might be barking up the wrong tree hoping fixing my evap monitor issue might fix my "virtual sensor" calculation problems.

In the end, I may just end up resetting it periodically with my Tech 2, anytime calculations get so far off base things start getting smelly when cold idling. It hasn't gotten back up into the high 30's (when running <10% gas) since I reset it the first time.

 

[kbuskill]

If your evap monitor is completing and you still are getting haywire ethanol calculations, I might be barking up the wrong tree hoping fixing my evap monitor issue might fix my "virtual sensor" calculation problems.

In the end, I may just end up resetting it periodically with my Tech 2, anytime calculations get so far off base things start getting smelly when cold idling. It hasn't gotten back up into the high 30's (when running <10% gas) since I reset it the first time.

I'm just confused as to why it recalculates it the following day.

I was under the assumption that once it detected a refueling event, of at least 3 gallons, that it went into ethanol relearn mode and that it took X amount of miles to complete the process and once it was done that was it.

Apparently my Burb didn't get the memo... lol

Like you though, once it recalculated the next day it kept that percentage for the remainder of the tank. Who knows.... I think GM shouldn't have cheaped out by getting rid of the physical FF sensor, or the cabin air filter for that matter.

 

[wsteele]

I'm just confused as to why it recalculates it the following day.

I was under the assumption that once it detected a refueling event of at least 3 gallons that it went into ethanol relearn mode and that it took X amount of miles to complete the process and once it was done that was it.

Apparently my Burb didn't get the memo... lol

Like you though, once it recalculated the next day it kept that percentage for the remainder of the tank. Who knows.... I think GM shouldn't have cheaped out by getting rid of the physical FF sensor, or the cabin air filter for that matter.

Yes, at least at this point, I would say the "virtual sensor" is kind of a lame substitute for a real sensor.

 

[wsteele]

I filled the Yukon up with ethanol free gasoline this morning on a near empty tank. After the running around I did (maybe 20 miles total), the virtual sensor settled on the value that I have 21.38% Ethanol in the tank (reality is less than 1%).

I will see what it says when I restart it later today, but definitely, something is not working in my virtual Ethanol sensor.

 

[kbuskill]

I filled the Yukon up with ethanol free gasoline this morning on a near empty tank. After the running around I did (maybe 20 miles total), the virtual sensor settled on the value that I have 21.38% Ethanol in the tank (reality is less than 1%).

I will see what it says when I restart it later today, but definitely, something is not working in my virtual Ethanol sensor.

What was the E % before filling up?

 

[wsteele]

What was the E % before filling up?

I think it thought I had 17% (the actual percentage in that tank was about 6%, tested with my bottle). I might be able to get some history data from my scanner and get exactly what it thought, but I think 17% is very close).

Edit: I know the definition of crazy is doing the same thing and expecting a different result, I was just hoping maybe with a fresh tank of zero, the sensor would start to get a clue on its own.