Cold start hesitation

ivin74 said:

Any updates? Just curious if you fixed the issue?

Have you verified the coils are good?
Look into the crank position sensor.

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Yes, issue was E85 as I initially had thought.

opfor2 said:

YES E85 is probably the issue for my 2011 which I ran E85 had a rough idle issue until I changed back to normal 87 gas nor she purrs like a kitten.

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A part of me wonders if it's the sensor in our trucks. I had reached out to blackbear tuning to ask them if they could make an e85 map or tune around the issues, and they said we'd have to install a physical sensor in our trucks. Stock, it's a "virtual" or something or another type of sensor, so it's not actually detecting the proper alcohol content.

Currently I switched gas stations to another blend of E85 and my truck fires up first time and drives smooth. I honestly just prefer it over 87 octane, even with the poorer fuel economy.

My 2011 Tahoe does not have a E85 sensor however I think my issue was that the ECM did not have the proper amount of time to recalibrate the alcohol content for I had a bad habit of refueling and then driving home which was not in the 7 miles needed to recalibrate. Like I said now that I switched back to normal 87 gas, I've had no further issues.

opfor2 said:

My 2011 Tahoe does not have a E85 sensor however I think my issue was that the ECM did not have the proper amount of time to recalibrate the alcohol content for I had a bad habit of refueling and then driving home which was not in the 7 miles needed to recalibrate. Like I said now that I switched back to normal 87 gas, I've had no further issues.

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Interesting, I did not know it needed 7 miles. That's quite a bit honestly. These trucks definitely seem finicky, definitely more than the GMT800's which I think had a physical sensor.

dwinters14 said:

Interesting, I did not know it needed 7 miles. That's quite a bit honestly. These trucks definitely seem finicky, definitely more than the GMT800's which I think had a physical sensor.

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From the owner's manual , page 9-74

it is recommended
that you add as much fuel as
possible — do not add less than
11 L (three gallons) when refueling.
You should drive the vehicle
immediately after refueling for at
least 11 km (seven miles) to allow
the vehicle to adapt to the change in
ethanol concentration.
E85 has less energy per liter
(gallon) than gasoline, so you will
need to refill the fuel tank more
often when using E85 than when
you are using gasoline. See Filling
the Tank on page 9‑75.