Terrible Fuel Mileage on my 2004 LLY

16DIRTY-MAX16 · 11-29-2012, 12:53 AM

I am having terrible mileage on my 04 LLY. By terrible I mean I am averaging 10.5MPG city. My truck has 341,000km with a LBZ Turbo Mouthpiece, AFE Stage 2 Intake, 4" Turbo Back Exhaust, EGR Delete/Blocker. Fuel Filter is new, the Fuel pressure regulator is new as well.

I need to get this issue dealt with ASAP. I sold my '01 5.3L Gas because I have a camper to haul now. I was getting 500Km to a tank with a 6" Lift and 35" tires with my gas truck, and now with stock size wheels on my '04 LLY I am barely getting 400km to a tank.

Any help is greatly appreciated!! I had a boost leak which I have since fixed, but it only added an extra 10km per tank... There are no other boost leaks.

P.S. Wasn't sure exactly where to post this, re-locate if necessary.

andy-stevenson · 11-29-2012, 01:50 AM

I'd check the air filter, the MAF sensor and for any fuel leaks, see if the injectors have leaking..

**usafracer** · 11-29-2012, 02:02 AM

Clean the mas air sensor.

**TheStepChild** · 11-29-2012, 04:13 AM

What tires and wheels are on it, psi too?

How long have you been checking or how long have you had this truck ?

What is the outside air temp are you idleing a lot and are you using block heater and grille cover for faster warmups?

16DIRTY-MAX16 · 11-29-2012, 07:33 AM

Air Filter is a brand new AFE Cone filter. I will clean the Mass Air sensor, and see what happens, as well as check for fuel leaks and let you know. I know there are no fuel leaks anywhere outside of the engine, but I will check the injectors. I have a set of 17" Eagle Alloy rims with 245/70R17 I believe. I am running them at 50PSI front and 70PSI rear. I have been using my block heater to speed up the warm-up and I don't idle very much. I have had the truck for 2 months.

duramaxallison · 11-29-2012, 07:40 AM

Checking for brakes hanging up wouldnt hurt either. Jack up each wheel and see if you can spin the wheel freely. You will have to raise both rear wheels at the same time.

16DIRTY-MAX16 · 11-29-2012, 07:45 AM

Alright, I will check all that this evening. And to correct I have 265/70R 17

95 Z71 · 11-29-2012, 07:48 AM

How do you check leaking injectors... My truck went form 15-16 in town to 10 in town.. air filter and fule filter are good.

duramaxallison · 11-29-2012, 08:13 AM

Quote:

Originally Posted by 95 Z71

How do you check leaking injectors... My truck went form 15-16 in town to 10 in town.. air filter and fule filter are good.

Have return rates checked or check for fuel in oil.

smokinu454 · 11-29-2012, 08:59 AM

I think i olny get around 12-13 in town but thats unloaded and all stop and go usually never over 30mph. what are your highway numbers looking like?

11-29-2012, 12:53 AM	eBay Motors #1 (permalink)
16DIRTY-MAX16 Junior Member Join Date: Oct 2012 Location: B.C. Canada Posts: 38	Terrible Fuel Mileage on my 2004 LLY I am having terrible mileage on my 04 LLY. By terrible I mean I am averaging 10.5MPG city. My truck has 341,000km with a LBZ Turbo Mouthpiece, AFE Stage 2 Intake, 4" Turbo Back Exhaust, EGR Delete/Blocker. Fuel Filter is new, the Fuel pressure regulator is new as well. I need to get this issue dealt with ASAP. I sold my '01 5.3L Gas because I have a camper to haul now. I was getting 500Km to a tank with a 6" Lift and 35" tires with my gas truck, and now with stock size wheels on my '04 LLY I am barely getting 400km to a tank. Any help is greatly appreciated!! I had a boost leak which I have since fixed, but it only added an extra 10km per tank... There are no other boost leaks. P.S. Wasn't sure exactly where to post this, re-locate if necessary. __________________ 2004 LLY Duramax Chevy Silverado 2500HD 4x4 CCSB Sinister EGR Delete w/ Finger Stick, 4" Straight Pipe, LBZ turbo mouth piece, PCV Re-route, AFE Stage 2 Cold Air Intake, Dual Red-Top Optima Batteries, Superchips Tuner, EDGE Jw/A CS, Iron Cross Push-Bar Front Bumper, 17" Eagle Alloy rims with Toyo Open Country Highway Terrains, 2 Post Extending Tow Mirrors, Escalade Colour Matched Door Handles Soon to come: 6" Lift, 16" American Racing Rally Rims with 35" Toyo Open Country All-Terrains, Iron Cross Rear Bumper, LED Flood Lighting under doors + Reverse light Flood Lights, 18000lbs Warn Winch, Lots of KC Lights

11-29-2012, 01:50 AM	eBay Motors #2 (permalink)
andy-stevenson Senior Member Join Date: May 2012 Location: Ontario Posts: 462	I'd check the air filter, the MAF sensor and for any fuel leaks, see if the injectors have leaking.. __________________ 05 LLY EFI Live Built Trans Built Front End Supporting Mods

11-29-2012, 02:02 AM	eBay Motors #3 (permalink)
usafracer Insert cool slogan here $usafracer's Avatar$ Join Date: Sep 2008 Location: North Pole AK Posts: 3,871	Clean the mas air sensor. __________________ 2010 GMC Sierra CC SB 4X4 6" lift and 315's 2008 GMC Sierra Crew Cab 4X4 (wifes) stock now... Zone lift going on and 305's
$usafracer is offline$

11-29-2012, 04:13 AM	eBay Motors #4 (permalink)
TheStepChild Creepy Join Date: Feb 2010 Location: Look out your window, see that van? Posts: 7,227	What tires and wheels are on it, psi too? How long have you been checking or how long have you had this truck ? What is the outside air temp are you idleing a lot and are you using block heater and grille cover for faster warmups? __________________ '07 LBZ '12 Express Van

11-29-2012, 07:33 AM	eBay Motors #5 (permalink)
16DIRTY-MAX16 Junior Member Join Date: Oct 2012 Location: B.C. Canada Posts: 38	Air Filter is a brand new AFE Cone filter. I will clean the Mass Air sensor, and see what happens, as well as check for fuel leaks and let you know. I know there are no fuel leaks anywhere outside of the engine, but I will check the injectors. I have a set of 17" Eagle Alloy rims with 245/70R17 I believe. I am running them at 50PSI front and 70PSI rear. I have been using my block heater to speed up the warm-up and I don't idle very much. I have had the truck for 2 months. __________________ 2004 LLY Duramax Chevy Silverado 2500HD 4x4 CCSB Sinister EGR Delete w/ Finger Stick, 4" Straight Pipe, LBZ turbo mouth piece, PCV Re-route, AFE Stage 2 Cold Air Intake, Dual Red-Top Optima Batteries, Superchips Tuner, EDGE Jw/A CS, Iron Cross Push-Bar Front Bumper, 17" Eagle Alloy rims with Toyo Open Country Highway Terrains, 2 Post Extending Tow Mirrors, Escalade Colour Matched Door Handles Soon to come: 6" Lift, 16" American Racing Rally Rims with 35" Toyo Open Country All-Terrains, Iron Cross Rear Bumper, LED Flood Lighting under doors + Reverse light Flood Lights, 18000lbs Warn Winch, Lots of KC Lights

11-29-2012, 07:40 AM	eBay Motors #6 (permalink)
duramaxallison Senior Member Join Date: Jul 2011 Location: Indiana, USA Posts: 612	Checking for brakes hanging up wouldnt hurt either. Jack up each wheel and see if you can spin the wheel freely. You will have to raise both rear wheels at the same time. __________________ 2003 LB7 2500HD ECSB -Edge Evolution CTS -MBRP 4" w/ 5"tip -Banks Ram Air -35w AGT 6000k HID's -5% tint allaround -285/75R16 Michelin LTX A/T 2s -300k miles and counting -Daily Driver

11-29-2012, 07:45 AM	eBay Motors #7 (permalink)
16DIRTY-MAX16 Junior Member Join Date: Oct 2012 Location: B.C. Canada Posts: 38	Alright, I will check all that this evening. And to correct I have 265/70R 17 __________________ 2004 LLY Duramax Chevy Silverado 2500HD 4x4 CCSB Sinister EGR Delete w/ Finger Stick, 4" Straight Pipe, LBZ turbo mouth piece, PCV Re-route, AFE Stage 2 Cold Air Intake, Dual Red-Top Optima Batteries, Superchips Tuner, EDGE Jw/A CS, Iron Cross Push-Bar Front Bumper, 17" Eagle Alloy rims with Toyo Open Country Highway Terrains, 2 Post Extending Tow Mirrors, Escalade Colour Matched Door Handles Soon to come: 6" Lift, 16" American Racing Rally Rims with 35" Toyo Open Country All-Terrains, Iron Cross Rear Bumper, LED Flood Lighting under doors + Reverse light Flood Lights, 18000lbs Warn Winch, Lots of KC Lights

11-29-2012, 07:48 AM	eBay Motors #8 (permalink)
95 Z71 Senior Member Join Date: Sep 2009 Posts: 777	How do you check leaking injectors... My truck went form 15-16 in town to 10 in town.. air filter and fule filter are good. __________________ 2005 LLY crew cab short bed, Red. Some stuff.. Smokin Diesel Performance Duramaxtuner.com

11-29-2012, 08:59 AM	eBay Motors #10 (permalink)
smokinu454 Join Date: Nov 2012 Posts: 6	I think i olny get around 12-13 in town but thats unloaded and all stop and go usually never over 30mph. what are your highway numbers looking like? __________________ (current) 2005 chevy 2500HD CCSB LLY 4X4 silver birch. K&N CAI,AFE Turbo mouth piece, 4" MBRP straight pipe DP back, Insight CTS, EFI Live tuned by tyler at Punisher Performance. (Sold) 2001 chevy 2500HD ecsb LB7 4x4,Pewter, 6" lift, 20" mazzi hulks and 325/60/20 terra grapplers, banks intake,MBRP 4" exhaust,PPE boost increase valve,insight CTS, and EFI by tyler at Punisher Performance.

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