04 TB EXT and POOR gas mileage

convincer253

Original poster
Member
Apr 4, 2012
15
Am a newbie here as i just learned of this site from"the other site"...thanks....I have tried every gas tip from the other site and still am only getting 14 mpg on the highway...what gives....Is there something im missing...What do i need to do to get the MPG up to where they need to be or should be....vehicle has 85000 on it and is my wifes and she drives like a granny but still cant get the mileage that everyone else claims to be getting...Any tips or advice would be greatly appreciaeted......thanks
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
A bad thermostat or partially clogged cat could cause low mileage. Does your temp gauge sit right at 12 o'clock? Ever have a SES light on? Plug change is due at 100K miles - you might consider doing those and changing the upstream O2 sensor soon if they haven't already been done.
 

convincer253

Original poster
Member
Apr 4, 2012
15
Have changed the t stat already and yes its straight up on the gauge....Plugs have been changed also with the 41-103's...Havent changed the cat convert or the upstream O2sensor...Is the Os sensor a hard change...got a part # for the sensor and maybe a how to or is pretty straight forward...take out..install new one and plug in...I think on the other site i read something about this sensor and there was some debate about which sensor to use...so if you can...let me know the brand and part# of the sensor and i can try that first...Im sure the cat convert is a pretty costly fix...correct....thanks
 

convincer253

Original poster
Member
Apr 4, 2012
15
Have never has a SES light either...not sure what it is...but have never seen it on the dash ....
 

Voymom

Member
Feb 3, 2012
2,523
I have an EXT envoy 03 and I get about the same gas mileage as you do on the highway. It sucks hardcore, but I think it's something we need to get used to lol
 

RayVoy

Member
Nov 20, 2011
939
19 to 20 driving at 60 to 70 mph should be what your seeing.

The engine needs to be in good shape (plugs, filters, o2 sensor, injectors, cat)

The rolling resistance needs to be as low as possible (tires without an aggressive thread, sufficient air pressure, correct alignment, brakes not dragging, etc).

Remove unnecessary weight (the truck, the liquids, you. remove everything else (including the mother-in-law))

Getting all of the above into shape will improve mileage
 

Mooseman

Moderator
Dec 4, 2011
25,335
Ottawa, ON
I'm getting 14mpg and that's after going to efans. I was much worse before. I also have change the camshaft actuator (not the CPAS) and probably the cat due to past owner neglect. Last summer I did get 16mpg but went down over the winter.
 

CaptainXL

Member
Dec 4, 2011
2,445
Getting 14 city and 18 hwy if I use cruise. My suspicion is that 05's are notorious for bad mileage because there was a power increase but no MAF.
 

Ace1875

Member
Mar 29, 2012
276
my EXT is full of junk kids and mine, 60-70mph i get 15-20mpg.

new AC Delco coils, plugs, o2 & CPAS, home made CAI, stock exhaust, removed and cleaned the throttle. CAT is a year old. have lifetime alignment and wheel balance deal from Firestone. new Moog upper and lower balljoints, sway bar links and AC Delco poly sway bushings.

if nothing else seafoam your SUV. i do it a bit differently then others. after letting the vacuum from the brake booster sip it 1/4 of the way, i let it chug the last sip and either let it stall or ask my helper to turn the car off, let it wet soak internally for 20 minutes. the remaining seafoam add it to your oil and change it after 50 miles. then start it and smoke the neighborhood. :thumbsup: (remember when u start it let it start on its own, meaning don't touch the gas till it starts then keep a constant 300rpm till smoke is gone.)

the remaining seafoam add it to your oil and gas and change it after 50 miles.
 

convincer253

Original poster
Member
Apr 4, 2012
15
whats the Delco part # for the upstream O2 sensor...and how hard is is to change(a DIY video or pics?)....and a part number for the CAT...thanks all
 

Ace1875

Member
Mar 29, 2012
276
convincer253 said:
whats the Delco part # for the upstream O2 sensor...and how hard is is to change(a DIY video or pics?)....and a part number for the CAT...thanks all

ACDelco 213-1698 (same thing as NTK from advance auto)

DO NOT BUY BOSCH.

View attachment 20109

View attachment 20108

headed to work so can't type DYI, sorry
 

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CaptainXL

Member
Dec 4, 2011
2,445
convincer253 said:
whats the Delco part # for the upstream O2 sensor...and how hard is is to change(a DIY video or pics?)....and a part number for the CAT...thanks all

Can be extremely hard to change if its seized in there. I had to take the heat shield off and use an 8 inch pipe wrench with a cheater bar to take my O2 out.
 

Sparky

Member
Dec 4, 2011
12,927
No kidding! When mine crapped (totally shut down, that was fun when the engine about dies going up a hill :crazy:) I spent a Sunday afternoon fighting with mine. Ended up borrowing the neighbor's huge pipe wrench to get it to come out. Had to remove a bunch of crap to get to it, although my heat shield is so corroded that it came out easily :biggrin: The replacement sensor was tight getting back in... I doubt it'll come out.

I used a Bosche even though they aren't recommended because I had to get the truck running again to go to work the next day and no one who was open had AC Delco or Denso in stock (Denso makes the AC Delco sensors from what I remember, there was a thread on the OS about that and they look identical). I have a Denso replacement that I planned on swapping out later, but surprisingly the Bosche has treated me OK unlike most people's experiences with them in GM vehicles. I'm saving the Denso for if/when I need a new manifold.
 

Ace1875

Member
Mar 29, 2012
276
Sparky said:
......I used a Bosche even though they aren't recommended because I had to get the truck running again to go to work the next day and no one who was open had AC Delco or Denso in stock (Denso makes the AC Delco sensors from what I remember, .....

no NGK does. Both my ACDelco O2 says NTK on it. and the only other place that has NTK in stock is Advance Auto Parts.
 

Sparky

Member
Dec 4, 2011
12,927
Drat :crazy:
 

Uncle Blazer

Member
Dec 8, 2011
263
14mpg hwy? :eek:

My EXT averages about close to 19 hwy, and the standard low numbers for city. Of course here in God's country, there isnt much for hills so it is pretty smooth sailing.
 

DenaliHD66

Member
Dec 4, 2011
597
For the longest time I've gotten 11-13 mpg, consistently, mix of city and highway driving. I moved a month ago, and I've gotten 14.8, 15.3, and last time I filled up was 15.6. No idea what caused the change, as I'm nearing an oil change. Only thing I can think of, at my old house, my street was a giant hill, so anytime I left, my truck would always have to climb up that thing when cold. It was about 1/4 mile long hill, whereas now its completely flat when I leave, so my truck is warmed up by the time I reach any hills. I mean if that's the case, then that's a huge difference, but nothing else has been changed with the truck.

The last time I got that good of gas mileage was about 5-6 years ago when I had the OEM size tires. I bumped up to 255/65/17 Bridgestone Dueler Revos and haven't come close to that since until now.
 

Ace1875

Member
Mar 29, 2012
276

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Sparky

Member
Dec 4, 2011
12,927
I want to see you do 30mpg uphill :raspberry:
 

Ace1875

Member
Mar 29, 2012
276
Sparky said:
I want to see you do 30mpg uphill :raspberry:

okie

***pulls out my horses and tie them infront of my TB**

**************Pics Coming Soon***************
:rotfl:


On a side note. whenever i buy tires i want the installer to tell me the force variation the balancing machine registered for each tire. lesser means smoother ride and more MPGs
 

CaptainXL

Member
Dec 4, 2011
2,445
Ace1875 said:
the last pic was the only one on an incline. the rest where on cruise on the Highway.

If i keep my HPR lower then 65 i get great MPG.

Well anyway...instant MPG has been proven to be unreliable at best. You need to use the odo+fill up method.
 

Sparky

Member
Dec 4, 2011
12,927
I recently got just a little over 21mpg out of my TB on a highway trip, but because I have the tiny 18 gallon tank in my 02 I only got a little over 300 miles before I filled it. But maybe that's a good thing, it isn't quite as big of a shock to the wallet at the pump!
 

DenaliHD66

Member
Dec 4, 2011
597
Sparky said:
I recently got just a little over 21mpg out of my TB on a highway trip, but because I have the tiny 18 gallon tank in my 02 I only got a little over 300 miles before I filled it. But maybe that's a good thing, it isn't quite as big of a shock to the wallet at the pump!

Up til recently I've only gotten around 300 miles (now 340-350) to a tank, and I have the 26 gal one. I wish mine was bigger actually.
 

khill

Member
Jan 7, 2012
86
Poor gas mileage:

O2 sensors (BIG difference if dirty)
Fuel filter (every 30k miles, got at least 2mpg when replaced mine after 60k miles :crazy: oops)
Plugs
Bad gas (use top tier and fill up in the morning, avoid when the tanker truck is there, stirs up silt)
Deflated tires >5psi
Low flowing (dirty) air filter


Big thing for me was driving habit... I used to constantly enjoy my PCMforLess tune, now I piss people off when taking off from lights. Not too extreme, but I'm just not in a rush to get anywhere. I got at least 2 mpg out of this one alone. I heard a good analogy from somewhere to "pretend there's an egg between your foot and the pedal".


I have a scangauge as well and it has never had a completely accurate read on my gas mileage. It's always off by about 3 up or down. I can't say the fill and divide method works completely either, I've apparently had 28 miles to the gallon on more than one occasion.


I am now getting about 18-20 reliably, though with gas prices lately, I'm also driving a lot less but that's another story...



Good luck,

Keith
 

Sparky

Member
Dec 4, 2011
12,927
I think someone fails at math :raspberry:
 

RayVoy

Member
Nov 20, 2011
939
khill said:
I heard a good analogy from somewhere to "pretend there's an egg between your foot and the pedal".



Keith
Good suggestion :thumbsup:

When I taught my kids to drive, I actually told them to pretend there was a glass of water on the dash.
 

Rubberman

Member
Dec 14, 2011
117
I changed the plugs, fuel filter, cleaned the K&N filter, Cleaned the Throttlebody. I have an EXT and i get 21-22mpg on the hiway.
 

plaen

Member
Dec 4, 2011
55
Uncle Blazer said:
14mpg hwy? :eek:

My EXT averages about close to 19 hwy, and the standard low numbers for city. Of course here in God's country, there isnt much for hills so it is pretty smooth sailing.

Wow, that is pretty bad, I get 14 hwy the 02 on 35" tires, and 21 hwy 17 city in the 07, bone stock, minus the transgo kit.
 

CaptainXL

Member
Dec 4, 2011
2,445
plaen said:
Wow, that is pretty bad, I get 14 hwy the 02 on 35" tires, and 21 hwy 17 city in the 07, bone stock, minus the transgo kit.

That's not bad at all. 19 Hwy for a '04 or '05 is correct. He has an EXT so they are about 2 MPG less than a SWB.
 

plaen

Member
Dec 4, 2011
55
CaptainXL said:
That's not bad at all. 19 Hwy for a '04 or '05 is correct. He has an EXT so they are about 2 MPG less than a SWB.

Should of specified, the OPs 14 hwy, lol.
 

jbones

Member
Dec 5, 2011
658
RayVoy said:
When I taught my kids to drive, I actually told them to pretend there was a glass of water on the dash.

How things have changed, when my dad taught me he told to pretent there was a pretty girl in a tight sweater waiting for me to pick her up.:biggrin:
 

Valetman23

Member
Apr 12, 2012
3
My TB is a salvaged was hit on the driver side replaced with a 15 or 16 gal tank and i get 280 miles per tank just seafoamed it runs great no change in fuel milage
 

DenaliHD66

Member
Dec 4, 2011
597
One thing that seems to help is to stick with the same grade of gasoline so the pcm can get used to it and use it most efficiently. I used to rotate a mid grade or premium fill up every month or so, thinking it would help my aging truck, but just the opposite is true. gonna get it reflashed for 93 premium grade though and see where that takes me. i'll have the efan installed and my first spark plug change so i hope there is a big difference.
 

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