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Old 09-20-2008, 08:58 PM
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Default poor gas mileage

[&o]Ok here it goes;i recently bought a 98 blazer with the 4.3 vortec engine....the vehicle has just over 116000 miles on it..it runs and starts fine, although it does seem to lack some power, but i noticed the gas milage was horrible..i get about 200 miles to the tank which is only 18 gallons, or about 11.14 MPG city driving!! I have rerplaced everything i know in a tune up,(fluid check, plugs, rotor, cap, wires, filters, including the fuel filter), added injector cleaner to the gas tank, nothing helped if only slightly, no warning lights on at all,any suggestions as to what is going on?, or is it justold age, LOL, any tests i can do, be specific please, what should the MPG be ??? Thanks alot for any help new old blazer owner..
Old 09-20-2008, 11:40 PM
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Default RE: poor gas mileage

Well you MPG is going to be off by some as the tank holds 18 but you shouldnt burn the last few gallons since it overheats the fuel pump. As for the mileage fixes does your engine warmup easily, or is it really slow like the thermostat is stuck open? What wait oil do you use in the engine and is it synthetic or conventional? Have you cleaned the MAF sensor and EGR valves? What RPM do you idle at when the engine is warm and is it steady? Also what kind of driving do you do mostly. My city mileage when I have to go to school is terrible due to stop and go traffic and lots of idleing in the parking garage. Its about 14MPG when im doing this if im only doing highway I can get 21MPG, and if its my work commute about 17MPG. My numbers are about average based the MPG poll here, but then again mine should be slightly lower due to the fact I have AWD.
1997 Olds Bravada AWD 4.3L Auto ~44000mi(high idle time), CAI, Quad Beam Mod, all Synthetics Fluids
Old 09-21-2008, 12:21 AM
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Default RE: poor gas mileage

i also get around 200 miles to the tank. i have replaced all the same things. so i dont know if this is normal or not. I do have 31" tires though
99 2 Door 4x4, mild built vortec 350, 33x12.50" BFG M/T KM2's, 2" BL, 6in superlift, tinted windows, Sony HU, flowmaster, 9500lb winch, custom front bumper
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Old 09-23-2008, 12:29 AM
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Default RE: poor gas mileage

ok i used 10w40 synthetic oil since the engine is so old, but the manual recommends 5w oil, the engine warms quickly and idles at about 500 to 600 RPM and is steady, i have not cleaned the MAF or EGR how do i do that and what do i use? i changed the PCV valve recently also it was pretty gummed up..thx for the replywaiting to hear back
Old 09-23-2008, 01:51 AM
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Default RE: poor gas mileage

Clean the maf sensor with the special cleaner you can get at any part store. I just bought a 97 and when you take off from a light it felt like i was pulling a boat or something. I cleaned it today and now i have all the power back. Try it
Old 09-23-2008, 08:34 AM
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Default RE: poor gas mileage

Although I dont have milage issues with my blazer, I had a '98 corvette that got lousy milage for about 3 years while I tried to figure out the problem. I did everything too it you could think of, including a new timing chain,and it would only average 16-17 mpg.

Then I changed out the O2 Sensors.
Overnight it went to 20-21 mpg.

The sensors where not throughing any codes, but obviously they where not doing well.

Just a thought.

My blazer gets 18 mpg average, with a good deal of highway driving.
Old 09-24-2008, 10:50 AM
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Default RE: poor gas mileage

ok guys ill give it a try and let you all know..thx
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