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-   -   Poor MPG, Stumped (https://blazerforum.com/forum/2nd-generation-s-series-1995-2005-tech-41/poor-mpg-stumped-54319/)

jbsnowboarder16 01-19-2011 01:41 PM

Poor MPG, Stumped
 
Hey guy's so here's whats up. My 2000 wit 89K on it has been getting terrible gas mileage over the last month or so. I'm talking in the range of 11-13 with a mix of city and highway driving.

About 15K miles ago, I changed all the plugs, fuel filter, and air filter. About 3 days ago I cleaned the MAF sensor and the EGR valve. I can't seem to figure out why mileage has been terrible.

I've even been under the truck looking for leaks and checked the transfer case and front axle to make sure there is no problem there (replaced that vacuum switch on the t-case about 25K miles ago, it was stuck and causing my mileage to stink)

Anyone else got any idea's on what I can check?

Debonair 01-19-2011 04:30 PM

oxygen sensor?

jbsnowboarder16 01-19-2011 05:22 PM

I thought of that... No Code though to tell

Benedict1337 01-19-2011 05:45 PM

my blazer gets that, its because its cold out you're going to see worse gas millage when its cold out. blazers don't see much over 15 mpg's unless you drive like an old man

jbsnowboarder16 01-19-2011 06:02 PM

It has never done this before though, normally in the winter it runs about 14-15 even with some 4WD, and it was weird because it got the normal MPG that I'm used to, and then it randomly started getting poor mileage over the past 3 tanks

streblo 01-19-2011 06:19 PM

Thats always a tough one when no codes are thrown.
With what you have done already is a good start. Only other things you can possibly check would be.
tire pressure (which is a duh), fluid levels. Other than that your starting to get to the end of things where codes would or would not be thrown, such as temp sensor, o2 sensors, and your cat plugging up. It is difficult but sometimes these things will start to malfunction but not throw codes, there might be some other threads here about how to check /bypass/eliminate some of these

jbsnowboarder16 01-19-2011 11:12 PM

Yea, tire pressure was one of the first things I checked. I think I may try the wires and the cap and rotor since they weren't replaced when we did the plugs... I don't want to try the "shotgun" approach. I just don't know :-\

streblo 01-19-2011 11:19 PM

if its not running to rough it might be a long shot, but you can check the cat by checking the back pressure. I would try the cap and rotor before wires. I burn up cap and rotors, i think i run through about 2 or 3 of them every 100,000km

ANOTHER THING you can/should check is your rear brakes!, dont know how this one skipped me. I HAD this problem before, for me it was the rear passenger. the caliper was not releasing properly and the brake was riding the whole time.....easy check is go for a highway drive then feel all the wheels and see if one is hotter than the other. or take the wheels and calipers off and inspect the sliders/pistons/pads.......I figured it was this problem after a) i blew up a pad. and b) on the highway i drove from edmonton to winnipeg without using my brakes once!......i downshifted with the tranny and coasted into stops and gas stations and saw the gas mileage slowly improve.

UberFail 01-20-2011 12:21 AM

hmmm what kind of mileage were u getting before this serious sudden drop?

i'm pulling an avg of around 17.5 mpg in my 97 jimmy slt with 280,000km's or 174,000miles PURE stock on winter tires - and avg temp here has been around 20's f or -5 c or colder (recently much colder) could your intake be blocked off or the filter clogged already?

marksoftball 01-20-2011 06:09 AM

Just a couple of thoughts.
Is your Blazer garage kept?
Do you fill up the gas tank at the same place?
Which octane to you use?
What kind of engine oil are you using?
I watch my rpm's more than I watch my speed.
And yes I drive like an old man especially during
winter time. 15mpg city 21-23 highway. Light on the pedal.

Mark

blazinloud 01-20-2011 11:53 AM

lets not forget extra rolling resistence, warm up times, very cold air, thicker oil, yada yada.

im going through about 10-15 liters a day! tough to keep up to that thirst when im not working.

UberFail 01-20-2011 12:08 PM

.... at that kinda rate - why the hell are u driving around if ur not working? stay home :P

closer 01-20-2011 01:21 PM

I don't know if there's any truth in it. But I always heard that there was a "winter-blend" gasoline. And I always heard you can't get as good of gas mileage with it.
I notice on my blazer when it's freezing out... It takes forever for my torque converter warm up and lock in. Before it does my overhead stays at 14mpg until it warms up and locks in. After it locks in... I'm back at the normal 17-18mpg. Mine's pretty wore being that I'm almost at 200,000miles. You wouldn't think that 500 sumthin' RPM's would make that big of a difference but it does.Oh... mine's garaged and not warmed up before I leave for work.

jbsnowboarder16 01-20-2011 02:24 PM

I averaged about 16-18 before it tanked about a month ago. IT isn't garage kept because I live in an apartment. I usually run 87 but when I noticed it dropping off, I ran 89, then 93 and put in a bottle of STP both times after running it almost empty, but alas none of that changed it. Actually when i ran the 93 through it dropped to 12.3 MPG instead of the 13.2 i was getting. I've gotten it at a couple of different places here around town that I usually get gas at with no problem, so that is why I'm thinking it is something with the truck maybe....

streblo 01-20-2011 02:44 PM

Ya, check the brakes first, when you get home feel each rim and see if one is hotter than the others.

jbsnowboarder16 01-20-2011 03:53 PM

Brakes are just fine

blueblazer1982 01-20-2011 05:18 PM

Catylic converter. especially if you are losing power and throttle response. take the o2 sensor out of its place just in front of the cat. if you get power back that cat is plugged. mine is plugged right now and my k5 gets better fuel economy then my blazer and i was averaging 17mpg before it started going downhill:icon_playing:

Debonair 01-20-2011 06:00 PM


Originally Posted by closer (Post 399943)
I don't know if there's any truth in it. But I always heard that there was a "winter-blend" gasoline.

interesting you mentioned this.

i saw this article on another board.

http://zhome.com/ZCMnL/PICS/winterGas/winterGas.html


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