New L83 Check engine light on with E85

[Zubadenzie]

Sorry if this has been covered elsewhere, but my searches always return 0 results....

 

After running out the dealers gas, I filled my new 2018 Z71 Crew with E85. I always used it in my 07 Avalanche and it ran great! After reading up on the HP and Torque benefits of using E85 with the L83 motor, I filled up with less than 300 miles on the truck.   Driving home, it ran great. The next day, I started the truck and the check engine light was on. The truck seemed to miss fire under low rpms and stuttered a bit when switching from V4 to V8 mode. Needless to say, I was unhappy. I assumed that maybe the Flexfuel I got may have had water or something in it. The remote start would no longer function either.

 

Yesterday I started the truck with nearly 450 miles and the light was off. Remote start working again. I took a 150 mile interstate trip with zero problems. Thinking that the water had evaporated or the truck's computer had decided that the flexfuel was ok or something, I drove until nearly empty. Filled up again with flex fuel at a different station, in another town, and finished the drive home (70 miles or so). No problems what so ever.

 

Later that day i got in for a quick trip to town, started the truck and there the check engine light was back on! Back to missfiring and stuttering.

 

What is going on? Did I get a lemon? Is this common? Do I need an exorcism? Any help would be appreciated.

 

Only mods I have done have been the Fog and reverse light/bed light diode mods.

[truckguy82]

Need the code to tell you anything

 

every single person who owns a car 1996 or newer should invest in a cheap ob2 scanner, even if you’re not doing the repairs.

 

just always better to be informed 

 

[Yondu]

Is your truck flex fuel capable?  It's an option on 5.3s 2015 and newer.  You are looking for RPO FHS. Is it's FHO it's not

[Zubadenzie]

Thank you! I'll check that when I get home. I'll post what it says.

[Zubadenzie]

Build sheet lists an 5.3L V8 ECOTEC3. When I looked up the ECOTEC3 the majority of the article referred to the enhanced E85 capability. I guess that's another thing I need to check.

[Yondu]

My 2018 5.3 is not. You can either scan the QR code in the door jamb to look for that RPO code I listed or I read that the flex-fuel ones have some sort of flex fuel sticker on the gas door. our trucks don't have gas caps anymore so it won't be yellow like it was at first. You can also check the window sticker it's a separate option that's $100

[Zubadenzie]

Thanks! I would have def paid the $100. Guess the salesman didn't know either. He popped the hood and said that the 5.3L V8 ECOTEC3 in the truck is E85 compliant. But, the RPO does show FHO! GREAT! I guess it'll get over this tank full too.

[ftwhite]

My guess is that the engine is compliant in all cases. Its the fuel tank, fuel lines, and such that need to be upgraded for $100 to handle the more corrosive effects of E85. Why it caused your engine to misbehave is interesting, and worth knowing (for the forum's sake) what code was being thrown.  

[Black02Silverado]

It would be interesting to know as well.  Our 2016 isn't FF and I run E85 in it with no problems.  Curious as to what is going on with yours.  Heck even my 2002 which is not FF runs fine with no issues and it has been using it for 2 years now.  Just might be some bad E85, especially if it isn't fresh and not a big seller from those stations.  It is amazing on how many people don't have a clue that the yellow cap means they can run it.  I talk to them all the time when I'm at the pump filling up and see that they have a FF vehicle and are using regular. They tell me they had no idea.

[Yondu]

5 hours ago, ftwhite said:

My guess is that the engine is compliant in all cases. Its the fuel tank, fuel lines, and such that need to be upgraded for $100 to handle the more corrosive effects of E85. Why it caused your engine to misbehave is interesting, and worth knowing (for the forum's sake) what code was being thrown.  

The $100 is for a sensor that tells the truck how much ethanol is in the fuel.  The more ethanol, the richer it needs to run (much higher quantity of fuel for the same operation.  Your truck has fuel trims to adjust and they're most likely pegged out to try and compensate, which is only getting closer to where it needs to be. Don't be surprised if after you put gas in it runs a little off for a while as it re-adjusts back down.  

 

No cause for concern for a tank or two, but obviously we're stuck with regular gas.  If you're willing to potentially void your warranty you can install the sensor and tune the vehicle. 

[Sierra Dan]

I bet your truck is not E85 capable.

 

Look on the lower corner of your driver's door window there is a sticker that says FLEXFUEL if its compatible. Or, check your glovebox RPO label (SPID label) and look for the following RPO code:

 

FHO: Vehicle Fuel Gasoline E10 (NOT a FlexFuel Truck)

 

FHS: Vehicle Fuel Gasoline E85 (FlexFuel Truck)

 

*courtesy of Newdude*

[thekevin]

My 2018 isn’t FF either and I ran one tank of E85 in it and had the symptoms as the OP. I am going to order the sensor and tubes soon to convert mine over.


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[swathdiver]

It's not a big deal to convert to add the sensor, in fact, there was a post on it here just the other day that was years old but had been refreshed.  

[TJay74]

On 11/19/2018 at 2:24 PM, ftwhite said:

My guess is that the engine is compliant in all cases. Its the fuel tank, fuel lines, and such that need to be upgraded for $100 to handle the more corrosive effects of E85. Why it caused your engine to misbehave is interesting, and worth knowing (for the forum's sake) what code was being thrown.  

 

Incorrect, the fuel system is the same across the board. The extra $100 is for adding the flex fuel sensor into the system and modifying the OEM tune to accept flex fuel. It is an easy fix to some degree, but it will cost around $500 now to convert over to FF.

[Bill Reinhardt]

What color is your gas cap?