NGK BR7EF Plugs on Stock Tuned 2013 Denali - now issues

[Letcher77]

Have a stock 2013 Yukon XL Denali. Put a 91 tune on it and it really woke up. Since 91 octane is getting extremely expensive and it doesn't get very good gas mileage I reached out to my tuner to see if it would be possible to reduce the tune so it could run on 87 octane. Tuner suggested I replace the plugs with NGK BR7EF and install a 160 t-stat so that it could run on 87 and shouldn't reduce the mileage much. I installed the plugs with a suggested gap of .030 but didn't have a chance to install the t-stat. Took the yukon out for a drive and when coming to a stop the RPM tends to drop and on some occasions the truck actually dies.

Just trying to get some thoughts on potentially what is going on here. Are the plugs too cold? Is the .030 gap too small (I know factory gap is .040)? I took the plug wires off again, inspected them and installed them making sure I heard/felt the click. I didn't replace the wires with new ones, so maybe there is a crack internally? I made sure to take the plug off only pulling on the boot/metal cover. I was very careful install the plugs and none of them were dropped. I really don't want to go through the hassle of taking them out to inspect the porcelain. No codes have popped up either. Anyone have any ideas?

 

[avalonandl]

Put the stock plugs back in. Chevk them after 500 miles.

 

[gooffeyguy]

Did your tuner make you another tune to run with the cooler Stat and other plugs? Like maybe one with less timing?

If not, can you install the stock tune?

I'd rather run a stock tune on 87 and just make sure to drive it like your grandma than an aftermarket tune made for 91

 

[Letcher77]

Yes he did. Had the same issues on that tune. Also, swapped back to the stock tune and still had issues.

 

[gooffeyguy]

Probably the plugs then.

I know your tuner probably wanted you to use a colder plug because it'd be less prone to detonation, but I'd still run the stock plug.

Do you have E85 in your area? Is your 2013 Flexfuel?

 

[CaptainAmerica1]

Time for a better tuner

 

[Letcher77]

Probably the plugs then.

I know your tuner probably wanted you to use a colder plug because it'd be less prone to detonation, but I'd still run the stock plug.

Do you have E85 in your area? Is your 2013 Flexfuel?

Yea it is flex fuel and I have e85 down the road.

 

[Foggy]

That gap is really tight for a stock engine...
Also, the 6.2 "likes" 91+ octane is bone stock form....
I'd put back in stock plugs with stock gap... Then run E85 if you can't afford
91 octane gasoline. You'll lose mph with ethanol but at least you won't ruin your engine

 

[swathdiver]

Have a stock 2013 Yukon XL Denali. Put a 91 tune on it and it really woke up. Since 91 octane is getting extremely expensive and it doesn't get very good gas mileage I reached out to my tuner to see if it would be possible to reduce the tune so it could run on 87 octane. Tuner suggested I replace the plugs with NGK BR7EF and install a 160 t-stat so that it could run on 87 and shouldn't reduce the mileage much. I installed the plugs with a suggested gap of .030 but didn't have a chance to install the t-stat. Took the yukon out for a drive and when coming to a stop the RPM tends to drop and on some occasions the truck actually dies.

Just trying to get some thoughts on potentially what is going on here. Are the plugs too cold? Is the .030 gap too small (I know factory gap is .040)? I took the plug wires off again, inspected them and installed them making sure I heard/felt the click. I didn't replace the wires with new ones, so maybe there is a crack internally? I made sure to take the plug off only pulling on the boot/metal cover. I was very careful install the plugs and none of them were dropped. I really don't want to go through the hassle of taking them out to inspect the porcelain. No codes have popped up either. Anyone have any ideas?

It's not that much of a difference moneywise in the grand scheme of things. Don't blow your motor to save $20.

The 2007-2008 6.2 L92s were tuned for 380 horsepower on 87 octane. Load that stock tune with your AFM turned off, everything else is basically the same.

41-162s are the current factory plugs or NGK TR5IX #7397, check the gap and make sure they are all set to .040". I just went through 2 sets of plugs this afternoon and most of them needed tweaking to be REALLY at .040".

Ethanol can be quite a bit less expensive right now compared with gasoline, even 91-93. These motors love the stuff. ALL 2009-2014 Gen IV 6.2s are FlexFuel capable.

 

[Letcher77]

It's not that much of a difference moneywise in the grand scheme of things. Don't blow your motor to save $20.

The 2007-2008 6.2 L92s were tuned for 380 horsepower on 87 octane. Load that stock tune with your AFM turned off, everything else is basically the same.

41-162s are the current factory plugs or NGK TR5IX #7397, check the gap and make sure they are all set to .040". I just went through 2 sets of plugs this afternoon and most of them needed tweaking to be REALLY at .040".

Ethanol can be quite a bit less expensive right now compared with gasoline, even 91-93. These motors love the stuff. ALL 2009-2014 Gen IV 6.2s are FlexFuel capable.

E85 is $4.60 a gallon and 91 octane at Costco or Sam's Club is $4.69. Unfortunately, E85 hasn't been inexpensive compared to gas for a very long time here in AZ.