Rough idle/ shuddering in idle.

[iboughtatahoe23]

When I cleaned throttle body it seemed it helped the idle the most in conjunction with using e85. Since then, I started using premium and one time I added gum out octane booster to an empty tank and filled it a bit over halfway with premium. Since then been running premium. Have only filled twice with premium tho

 

[Dustin Jackson]

@iboughtatahoe23 Running higher octane fuel is great but unless your Tahoe is tuned to take advantage of the high octane you might not be getting your moneys worth yet. Tune it to run on 91 and raise the idle and I’m sure you’ll be happy

 

[iamdub]

Actually i recall usually only using e85, and then I started using premium 93 and the idle got Worse.
I’m confused now, so run e85: The cheapest gas available… or run premium??

I feel like using premium may be the issue. I could be wrong.

In the mean time I’ll do plugs and wires

These things, in stock form, do better on 89 or higher, especially in hot weather. And, yes, the cheaper E85 can be better than 93. You'll get up to 30% worse MPG. But, if the price of E85 is 30% or more LESS than 93, then you're coming out ahead as far as cost. You'll just have to refuel in 300 miles instead of 400.

I could be wrong. But, based on your descriptions, I still believe you're referring to the common/normal shudder these have and you might be disappointed after firing the parts cannon at it.

Also, the brand of fuel can make a difference and, even then, it seems to vary by location. In my parts, Shell seems to be crap and Exxon and Chevron/Texaco seem to be the best choices.

 

[iamdub]

@iboughtatahoe23 Running higher octane fuel is great but unless your Tahoe is tuned to take advantage of the high octane you might not be getting your moneys worth yet. Tune it to run on 91 and raise the idle and I’m sure you’ll be happy

I know what you mean, but these things kinda ARE tuned from the factory to benefit from 89 or higher. They "adjust down" for the lower octane but are happier starting at and/or "adjusting up" for the higher octanes, including E85, if capable.

 

[iboughtatahoe23]

These things, in stock form, do better on 89 or higher, especially in hot weather. And, yes, the cheaper E85 can be better than 93. You'll get up to 30% worse MPG. But, if the price of E85 is 30% or more LESS than 93, then you're coming out ahead as far as cost. You'll just have to refuel in 300 miles instead of 400.

I could be wrong. But, based on your descriptions, I still believe you're referring to the common/normal shudder these have and you might be disappointed after firing the parts cannon at it.

Also, the brand of fuel can make a difference and, even then, it seems to vary by location. In my parts, Shell seems to be crap and Exxon and Chevron/Texaco seem to be the best choices.

So keep using premium? Seems to last longer. But I didn’t notice the shuttering happening more until after I started using premium. Which makes me want to use e85 again

 

[Marky Dissod]

... yes, the cheaper E85 can be better than 93. You'll get up to 30% worse MpG.
But, if the price of E85 is 30% or more LESS than 93, then you're coming out ahead as far as cost.
You'll just have to refuel in 300 miles instead of 400.

Actually, since E85 burns cleaner (less carbon deposit buildup) in the long run, it might be ok if the E85 is only 25% less than 93. Your call.

... didn’t notice the shuttering happening more until after I started using premium, which makes me want to use e85 again

Long story short: use more E85 as your wallet allows.
(Considering doing the same myself.)

 

[Onlyone]

I know after this second tank of E85 my Denali runs a whole lot better than with 91. I don’t even have to barely push the peddle for it to move down the road.

 

[iboughtatahoe23]

I know after this second tank of E85 my Denali runs a whole lot better than with 91. I don’t even have to barely push the peddle for it to move down the road.

I got an exhaust leak. My Tahoe is slow.

 

[Onlyone]

I got an exhaust leak. My Tahoe is slow.

Lol. Mine is slow too just a little bit faster than a Tahoe. I would definitely run E85 if I were you.

 

[kevlac]

OEM plugs and wires will do wonders for you. Start with those first! I had the same issue. I was having shudders to the point that I thought the torque converter was going bad. The dealership told me my plugs were good ( without looking at them) and wanted to sell me a transmission. I went elsewhere to have the plugs and wires changed. The plugs were bad! The electrodes were worn away on a couple of them. The truck has driven like a dream since then. No more shudders. Like you, before my plugs were changed, e85 seemed to make it shudder less. Nonetheles, stop chasing this and get those plugs. At your mileage, you need them anyway. OEM only!