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Super Crapy Milage.......


JoeyDBabe
08-18-2005, 06:30 AM
Ok, about 6 or 8 months ago, I was looking for a larger truck to pull my boat with and do family outings, trips, and shopping with. A used suburban seemed a perfect solution and way cheaper than the giant diesel, crew cab, 4x4 monster I originally wanted. I found a great condition 1998 Suburban LT, 4x4, Vortec with every option known to man. 150,000 miles, but a new transmission, a great set of tires and wheels on it and a 7500.00 price. I took it to my mechanic,(also a Suburban owner) we did a once over and knew what it needed to be a good, solid, dependable truck. I wrote a check and drove her home. The next day, a new fuel pump, (the old one sounded like a fighter jet warming up on the runway). A power-steering high pressure hose was put in and a complete flush and changing of the fluids, oil, transmission, transfer case, differentials. Hell, I even changed the air in the tires. Man, was it cool to be driving a V8 again and the sound of those Magnaflows made me feel like Bob Bitchen!. My wife took a liking to the new truck, especially after she smashed up my Lexus. I soon realized every time I drive the suburban it needed gas. So, like any good husband, I would fill it up for my lovely wife. Damn that 45 gallon tank was a gang of money at the pump. Checked the mileage tank and tank again. F#%kin 9! 9 MPG, no way! Way! The lil woman and myself aren’t kids anymore, I have had 2 birthdays that start with a 4. so we aren’t jamming around town with the pedal buried in the floor, in fact we both drove the truck so very timid in an effort to leave as many dinosaurs in the ground. I replaced a mass air flow sensor and 2 of the O2 sensors. Still shit for mileage. OH Ya gas is 3 bucks in Southern California! Were talking 130 bucks at the pump to go about 380 miles. Then the other day, a guy at work has the same truck. Same year, same LT package with 4 wheel drive, and 155,000 miles. He gets 16 MPG! What’s the gig? That’s almost twice what mine is getting. TWICE the Mileage! Anyone got a clue to what is an answer? At 3 bucks a gallon the cost of changing out a handful of sensors or replacing a few items doesn’t seem so bad. Can anyone tell me where I should start? Besides not driving the beast at all. The darn truck runs good, no codes, strong and the trans is solid. It’s a Chevy, a handful of ticky tack crap that is screwed up like the wiper motor, a power window switch broken in locked, or a tricky rear passenger interior handle or dim low beams. It’s a Chevy! Truly it is a solid truck, barley a squeak or rattle. Just unbelievably crapy MPG.

Thank you in advance for your reply.
But please hurry before the Chic at the gas station thinks I have a thing for her!

Dirtsled
08-18-2005, 08:56 AM
9mpg! Should have an 8.1L under the hood getting that mileage.

No codes, or other issues, runs fine? One very obvious thing I would check is make sure your not driving it in Auto-4WD, that was an option in 98 correct? My 99 has it.

Otherwise I can't think of much without more clues.

hazzzmattt
08-18-2005, 09:11 AM
like he said..no codes, or other issues, runs fine? make damn sure this thing is going into OD. you mentioned that tranny to many times for me.

trappie
08-19-2005, 12:24 PM
does it smoke like it is running extra rich? I had a similar problem on a V6 minivan and it turned out to be some sort of fuel pressure regulator (as best as I can recall) that was basically dumping way too much fuel into the cylinders.

84fiero123
08-19-2005, 07:46 PM
if no codes are comeing up it sounds strange a sensor gone bad is not out of the question but not what i would think. one thing that can to mind was brake dragging. i have an 86 to wheel drive that was makeing a clunk that i couldnt find untill i found i had a egg shaped drum. but in your case a dragging caliper or emergency brake would give you bad mileage. just a thought.

84fiero123
08-19-2005, 07:50 PM
ps
i forgot your not driveing in 4 wheel drive all the time are you?
or is it all wheel drive on yours. eather way just run it in 2 wheel drive is what you want if you arent already.

gaytrey1987
08-19-2005, 11:18 PM
Ok, I dunno if you have the new Takamitchi or whatthe whosits japanese 454 or what in your truck, but I drive an 89 SLE GMC with a 454 TBI, and when I bought it I got 19 miles per gallon out of it. After putting through some crappy gas, I ended up getting 4mpg. Here's what you do to improve gas mileage on a suburban:

Change the fuel pressure regulator at 100,000 mi.
Change the pickup springs in the distributor (if it has one, may be electronic ign.... kits to tune electronic and kits for distributor pickups are available at your local AutoZone)
Put in AC/Delco Spark Plugs and factory wires.
And if possible, have the computer chip reset or replaced with one programmed specifically for economy.

My 454 Burban has had all this stuff done to it....its getting 22MPG on the highway right now, 21 with the AC on and the stereo cranked (it takes alot of power to crank out 3500 watts!) Give that a shot, may not work so good for you, but you never know.

TTYL - BILL

gaytrey1987
08-19-2005, 11:21 PM
Another way to improve your gas mileage is to buy a Geo Metro instead!

Disgraceful, aren't I? I drive one of those too, and if I hadn't had it for years and know better, you'd think its a POS because its all ugly and beat up and crap.. anyway, laterz

JoeyDBabe
08-20-2005, 02:58 PM
like he said..no codes, or other issues, runs fine? make damn sure this thing is going into OD. you mentioned that tranny to many times for me.


She is going into Overdrive with a solid smooth and clean shift. Possibly I mentioned the word "transmission" because I just plunked down 2K last week for a rebuilt A4LD in my Old and Trusty 91 Ranger 4x4 Extra Cab 4.0L with 160K. Let’s say I am very transmission aware these days.

Thanks for the thought, I just filled the beast up again last night, "Can I barrow some money"

JoeyDBabe
08-20-2005, 03:10 PM
does it smoke like it is running extra rich? I had a similar problem on a V6 minivan and it turned out to be some sort of fuel pressure regulator (as best as I can recall) that was basically dumping way too much fuel into the cylinders.


Breaks are great. No draging. I did have a panic stop a few moths ago at freeway speeds that was a lot fun. that giant truck slipping and sliding, and going side to side, with smoke out of the tires was an E ticket ride. Damn Cell Phoners!

JoeyDBabe
08-20-2005, 03:17 PM
ps
i forgot your not driveing in 4 wheel drive all the time are you?
or is it all wheel drive on yours. eather way just run it in 2 wheel drive is what you want if you arent already.

Triple checked last night, i have the model with 4 buttons on the dash. 2WD 4Hi Neutral 4Lo. switched from gear to gear with that clunk and the transfer case engaged like it was on the showroom floor.

thanks,

crownedroyal
08-22-2005, 09:59 PM
Might want to try a honda civic. i hear they get 55 mpg.
my burben gets about 14 mpg in the city and i have a heavy foot, the tires that i have to put on the back every other week is more of a concern than the fuel mileage. :)

Old Dave
08-23-2005, 11:56 AM
Is the engine coming up to the correct temperature? A thermostat that is opening too soon and not letting the coolant get hot enough will cause it to burn more fuel. Maybe not that much more but it's something to check. I have a 97 GMC Suburban 1500 4WD and it gets 16.5-17.2 on the highway not pulling anything. I have the same engine and transmission as yours.

Dirtsled
08-25-2005, 09:06 AM
Breaks are great. No draging. I did have a panic stop a few moths ago at freeway speeds that was a lot fun. that giant truck slipping and sliding, and going side to side, with smoke out of the tires was an E ticket ride. Damn Cell Phoners!


Got to LOVE, panic stops in these pigs.

Reminds me of rodeo sex: you know get behind the beautiful wife, grab her chest and whisper in her ear, "ooh this feels much better than your sister/best friend," and then try to HANG ON!

(I know I know, but I love to use that one whenever I can...)

DDotson
08-25-2005, 07:07 PM
Take it to your GM dealer and have the EGR valve checked. The EGR may not always come up on codes but it will darn sure kill the fuel milage.

sub006
08-26-2005, 12:00 PM
Contact Van Gordon and Brown in Claremont, California. They have a Clayton dyno and all the latest GM software. Scott Brown will trace, find and correct any problem(s) affecting your vehicle's efficiency.

In the case of my 383 swap, he erased all the 350 codes and started over, reprogramming every 500 rpm or so on the dyno and on the road. Among other things he found my distributor advance was coming in 1000 rpm too late and the hot air warm-up valve on my air cleaner was stuck half-open.

In terms of drivability, performance and mileage my truck is transformed. These guys are not cheap but they will make your Suburban dance.

custmguru
08-26-2005, 03:40 PM
sure makes me feel better about my 11.5MPG to 12.5MPG.

what engine do you have the 350 or the 454?

JoeyDBabe
08-26-2005, 11:06 PM
Take it to your GM dealer and have the EGR valve checked. The EGR may not always come up on codes but it will darn sure kill the fuel milage.

Thanks to all of you for the comments and suggestions.

[B][COLOR=orange][FONT=arial black] What is an EGR Valve?

I am more than willing to buy and switch out some parts in an effort to fix this thing, but taking it to the dealer is an idea I can not entertain. It’s like saying here is a credit card, let me know when it stops working and maybe we will have a solution. Honestly, what can they do for a well out of warranty truck that my mechanic can’t?

JoeyDBabe
08-26-2005, 11:58 PM
Contact Van Gordon and Brown in Claremont, California. They have a Clayton dyno and all the latest GM software. Scott Brown will trace, find and correct any problem(s) affecting your vehicle's efficiency.

In the case of my 383 swap, he erased all the 350 codes and started over, reprogramming every 500 rpm or so on the dyno and on the road. Among other things he found my distributor advance was coming in 1000 rpm too late and the hot air warm-up valve on my air cleaner was stuck half-open.

In terms of drivability, performance and mileage my truck is transformed. These guys are not cheap but they will make your Suburban dance.

This sounds like a road to a solution. Do you have a number for this guy?

JoeyDBabe
08-26-2005, 11:59 PM
sure makes me feel better about my 11.5MPG to 12.5MPG.

what engine do you have the 350 or the 454?

350, dont make any sence, does it? :screwy:

sub006
08-28-2005, 10:18 AM
Hi, Joey!

Scott Brown's business 'phone is (909) 626-5232. Address is 150 Olive, #B in Claremont.

They needed my truck for two days (there is an Enterprise rental offfice about two blocks away).

Good luck and cheaper driving!

DDotson
08-29-2005, 05:12 PM
The dealer has the proper equipment to test everything. Most garages do not have the same equipment. A diagnostics will determine if there is something wrong. No I do not work for a dealership in anyway. I work for Hershey as a mechanic. I do most of the work myself on my truck but have found the dealership diagnostic test to prove very useful. Most places only charge 40 - 70 dollars a lot less exspensive than guessing and replacing parts that are in otherwise working order. Not to mention the time and aggravation involved in replacing them. That is how I found out about my EGR, that was slow reacting to acceleration which in turn killed my milage. I went from about 7 mile to the gallon make up to 16.

DDotson
08-29-2005, 05:14 PM
Oh sorry EGR is Emision Gas Recirculatory valve.

joelseeley
08-30-2005, 09:07 PM
Get One With A Diesel, I Did, Gets 23mpg Cty

joelseeley
08-30-2005, 09:10 PM
no its exhaust gas recirculation valve

sub006
08-30-2005, 09:57 PM
Diesels are cool, especially with turbos.

Only problem is, Joey is in California where GM light truck diesels are illegal.

custmguru
10-21-2005, 03:21 PM
350, dont make any sence, does it? :screwy:
it makes even less now. im getting my 11.5 to 12 in a 454.

Jimbozcrazy
03-14-2012, 06:48 AM
Sounds like I have the same issue with my 99. I got a 1500 with a 5.7 and the same 4X4 getting 10.2MPG in the city and I'm driving like Mother Theresa. Can I get an egr valve at autozone? I feel like I'm single-handedly supporting some middle eastern oil ministry every time I fill the bottomless 40 gallon tank.

I got no codes, no warning lights, and it runs like a champ, a very thirsty and parched champ!

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