Did you "do the math," or are you going by the DIC?
@RDF1 or @06MonteSS may have and answer for you.

 

I've logged math for the past few months- I figure the computer is bent out of shape since doing the delete so I never trust it.

 

Check tire pressure
Turn off A/C
Lighter weight engine oil
Turn off daytime running lights
Wash the truck
Install any missing skid plates / splash guards
Buy fuel from a different location / brand (fuel quality and MPG varies by location)
Remove aftermarket exterior add-ons (bigger mirrors, etc).
Revert to OEM tire size
Independently verify fuel mileage (top off tank, drive on freeway, top off tank >> do math)

 

Tires are well kept
AC rarely runs
I run 0w20
Been washed probably 20 times since this happened
No plates missing
Fuel has been bought several spots shell VPOWER seems to be the best
Nothing aftermarket except the tires (which still arent big enough to tank mpg this much.)

I have not independently verified yet but I will.

 

Without seeing a datalog or a lot more info its hard to help.

BTR stage 1 delete means what?

 

BTR Gen V 14-18 5.3L L83 DOD Delete Kit w/ BTR Low Lift Truck Cam Kit

This kit fits vehicles with the 8th digit of your VIN number "C" DOD Kit Includes: BTR L83 5.3L MLS Head Gasket Set BTR Lifter Trays - Set of 4 Delphi Gen V Non-DOD Lifter Set of 16 (NO WARRANTY) BTR Head Bolt Set 11546959 (19pcs) & 11611976 (1pc) GM Crank Bolt 11547372 BTR Exhaust Manifold...

tristarracingproducts.com

Gen V 14+ L83 L86 DOD Add-On Parts Kit

These are recommended items to replace when deleting the DOD/AFM from your 2014-2019 GM Truck or SUV with the 5.3L L83 or 6.2L L86. These items generally do not come in the delete kits but are the other parts that are recommended to be replaced while you are doing the delete. This kit includes...

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Here's the kit I bought.
I could ask the tuner if he can send me logs if that'd help.

 

Get a diablosport and a tune from DiabLew

 

I emailed lew and he mentioned not being able to do anything since it was already tuned.

 

Did the tuner just get the idle sorted out or did he spend several hours on it getting fueling sorted out?
Or did he just throw it into MAF only mode and send you out the door?
Lots of sketchy "tooners" out there these days.

 

I believe he ran through the whole thing. He was having issues at WOT so ended up replacing a dud wire which fixed it. When I brought it back to him a second time he mentioned something about trying to readjust the timing, as well as a few other things like idle ect to dial everything back and try and help. Koza Performance in IL, he knows his stuff(apparently). Trans tuned as well so Id assume it got the entire rundown

 

BTW.....Shell Top Tier gasoline is the worst you can buy. Too many additives.
That's pretty common knowledge on this forum....brought to you by Lew.....@06MonteSS

 

Worst gas is Irving or Arco. Bucees is pretty bad too.

Shell is good gas.

 

That's absurd mileage! I don't read/hear too much about people deleting gas emissioned vehicles. Stupid question, but your brakes aren't dragging, are they?

 

Not stupid. Had this issue on my old truck! But I wish it were that easy- replaced all brakes not too long ago, everything functioning nice and good.
Its about deleting AFM/DOD

 

I can tell you LTFT are disabled. Alcohol was sitting at 10 when cruising based on a couple screenshots i took last time i was trying to diagnose. Trims were a little whack but he said it was "de-cell" fuel that was causing a STFT spike over 25 as it only happened after leaning back into the pedal when coasting. I'll include a couple screenshots I took a while back. I can collect more information as well.

 

I hope I'm wrong, but this may be a tough one to pin down Hopefully someone here can point you in the right direction. Let us know what you come up with.

 

Yeah, he's had it tuned before already by someone else using hptuners tuning software... You'd need to get the truck ECM & TCM modules flashed back to the factory stock GM programming, then you could use a diablosport programmer on it and get a custom tune done...

Doesn't sound like that guy did a full tune really... Did he do driving data logs, and adjust your airflow/fueling by rescaling the MAF sensor for how the truck is running??

What are your average long term fuel trims for bank 1 and bank 2 ???

etc. etc... could be different things...

BUT - Make sure you are using GOOD gas, it makes a difference... Mobil, Exxon, Sunoco, Amoco, BP, Chevron - are the best brands to use...

NEVER use Shell, walmart/sams club/bj's, mom-n-pop, or no-name brands, as it's crap gas/additives that tends to cause a lot of knock retard and less performance/mpg...

Once people switch, they usually notice better mpg, better response/performance, etc...

Also, a lot of people tend to get better mileage with higher 91-93 octane gas...

 

Ive gone through all the fuel companies in every octane for testing purposes. Ran them all consistently for a month and nothing has ever changed. LTFT are disabled completely. He told me he did a full street tune on it. I did ask for data logs

 

Looking at the totality of this thread few things stand out.

The wheels and tires are going to impact your mileage plus the lift that is 1-2 gone right there. More air under means more drag and the increase unsprung rotational mass is going to have the biggest effect especially the tires.
The tune is definitely going to have an effect.

A lot of what Lew mentions could be your issue... What E10 are you using 87, 89, 91 or 93? What is the tune setup for?

See if you can get some ethanol free fuel and see if it has any change. The removal of ethanol should see a boost in fuel economy also.

 

Ive gone through all the fuel companies in every octane for testing purposes. Ran them all consistently for a month and nothing has ever changed. LTFT are disabled completely. He told me he did a full street tune on it. I did ask for data logs

 

Ah, so he did a speed density tune on it... why?? You don't have a monster build over 600/650+ hp, so a speed density tune is not necessary at all... You want to use the MAF sensor and long term fuel trims to adjust airflow/fueling, by re-scaling the MAF sensor table...

My educated guess is on a fuel issue, and that tune that was done...

 

I’ll see if I can get the logs and maybe something catches someones eye

 

This would be a good time to get your own tuning software.

 

Yeah, I thought about it, but BTR had told me strictly dyno or street tunes no flash tunes so I never bought a Diablo or anything

 

Bigger/heavier tires will hurt your mileage, as others mentioned. What gears are in the truck? Tall tires and tall gears is not a good combo. Was the speedo corrected for your taller tires? If not, your calculations are going to be way off.

 

yeah, forgot about that too.. bigger, heavier wheels/tires will kill mileage... and as RedSLEd mentioned, if they did not calibrate your tire size correctly to correct your speedo, then that will also definitely contribute to the issue...

 

i know its not the solution to the actual problem of a massive drop in mpg for a mod that shouldnt have, but you will get much better MPG at 60-65 rather than running 75 the whole way.

 

 

Any load in the bed, and is it covered? A bed cover gives much better aerodynamics. . . .

 

Bed covered beds are marginally better aerodynamically. The cab already stands in the way of the bed plus the bed creates a pocket of turbulent air that keeps the air flow off the tailgate. Adding a bed cover the biggest gain you will see is in noise reduction that the bed creates which is hardly detectable under 80mph. When you start getting faster the buffeting sounds if you pay attention gets a little louder but these trucks have a lot of sound dampening either way. Adding a bed cover made such a little change in fuel mileage I could argue that my driving style has more noticeable effect of fuel economy than the bed cover.
Bed covers are just good for turning your bed into a trunk and looks. Honestly that is why I got mine to carry stuff in the bed and have some barrier for weather changes.

 

I see most car tuners that tune trucks never get the TCM speeds corrected for whatever reason as well.

 

I could see that happening for sure. Still waiting to hear back on some data logs

 

bed is covered

 

What is your rear diff ration? 3.08 or 3.42 or did you change it?

 

3.42

 

285/70/17 keep them at 37psi. Its leveled with loaded struts, but the cam is a low lobe. Ive seen guys on Facebook pages with a 4+in lift with stage 2 and 3 cams getting better city mileage that I do highway. While I understand where your coming from, I dont think this is the culprit.

 

I mean I'm one of them. I've got a BTR stage 2 Kit, DOD delete, big ugly aftermarket steel bumper, 2 inch level, 275/75/18 tires, mildly worked heads, high flow aftermarket exhaust- and I still get 15- 16 on the highway (17+ if i have a tailwind lol) and 12 or 13 around town on my 2008 crew with the 4l60e. Heck I get better highway mileage than you're getting Towing a 3,000 lb plus load.

I wish you good luck bro, hopefully you can get it all sorted out, I'm sure it's something stupid.

 

Ah yes, that makes more sense. I would believe it but im still filling up 2/3x per week. I guess yeah, the Mpg calculations could be off, but my range is probably 250 miles on a good tank when I drag it to the gas light

 

Is there something going on with the intake gasket on the bank showing a misfire? My thought is unmetered air getting by the gasket is causing the STFT spike. Hard to tell without LTFT. Have you pulled the plugs to see if there are any variations between cylinders or banks? Good luck man. This sucks.

 

I checked and no vacuum leaks. Thank you i hope so too lol

 

Sounds to me like the cam is advanced. Did you degree it when you put it in?

 

I did not- cam runs pinned 1:1 with the crank as im sure you know, so you'd have to explain this to me.

 

If it ain’t broke… Stock 2014 5.3