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  1. #11

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    In the summer I tow a Crestliner 1850 Sportfish. Good size boat, and I expect to get bad mpg's. But most of the time the truck is running bare.

    I do use regular gas. I get it at SA, Holiday or BP. The truck does idel smooth. No hick ups. There is hesitation when I punch it. Takes a short period of timefor the motor to "catch up" I guess you can say. When I go to start it, it lights right now.

    I have been looking into a programmer but I just don't understand how it can loose it's programming.
    I do have a Viper car alarm/starter installed on it. That wouldn't cause anything.

    I needed to replaced the hubs for the ABS system to work again.
    Tim - Minnesota
    1997 Chevy Silverado ext cab
    4.3lt Vortec
    Few things added, nothing special!

  2. #12
    Master Mechanic
    lancer's Avatar
    Join Date
    Aug 2009
    Location
    Farmersville, Illinois, United States
    Posts
    611

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    my truck is an 06 fullsize 4x4 with 4.3L v6 and it gets around 16-19 just plain running and 21-23 if i actually put a full tank and drive the high way.....if that helps any


    2002 Tahoe LT---------TINTED WINDOWS------------7" DUAL DVD INDASH

  3. #13

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    Mine did to. My company truck is a 2004 - 4.3 full size and I beat the snott out of that truck. I speed every where I go. I keep that peddel to the floor and still get an average of 16+. Im looking at reprogramers but I don't how well I'm going to deal with the disappointment when it dosn't work.

    I installed the K&N air filter and just topped of the tank. I"m now down to 8.6 MPG.

  4. #14

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    My dad live's240 miles away in Northern Minnesota. Went there this weekend. Put old air filter back in but I wrapped duct tape around 1/3rd of filter reducing the amount of air flow thru the filter. This was to test my vacuum leak theory. Went 240 miles and only used 1/2 tank of gas. Im on the right track.

    Caddiac, some of the stuff you listed was checked. I am looking for the vacuum leak. The tranny was replaced. I need the tranny checked for it's shift pionts. I think it shifts to soon. Coolent level, thermostat, brakes and fuel pressure have been checked or replaced. Cat was checked by testing back pressure. No black smoke when I rev the engine. I know there is no cat or underware in their, maybe a few beer bottels.

    I want to thank everyone who posted replys. Your help has been pricless!!

  5. #15

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    Quote Originally Posted by snowmen88 View Post
    Do you mean like a K&N air intake?

    The tires are due for replacement. I'm going to put the stock size back on. I'm also removing the glass pac and replacing with the OE muffler. As far as the programming I will have to find someone in the St. Paul area with a programmer and pay them to do it. I want to see if the muffler and tires make a differance.

    "The main problem is that you have a V6 in a full-size truck... "

    Yeah it's V-6 but it had more than enough power for what I hauled or towed. Plus, I bought it new and bought it for 13K less then sticker. Great deal!
    Tritonboulder might be an ass but he's about spot on, lol. but before dumping a bunch of unnecessary cash into programmers and intakes and such, i would see what happens when you take it back to stock tires/exhaust. that is unless you want to try and sqeeze some extra out of her later. but you need to fix the problem first, not cover it up...those techs are probably right about the glass pack and tires. the other things the guys on here have come up with are all good too. and yes V6's are great for daily hauler work trucks, there's nothing wrong with them. hell, the new camaro's v6 makes more hp stock than most of the pre2007 V8's on this forum... if its all you need, then thats all you need. other than that, out of all that stuff that you listed, i'd have a close look at the cat again. the older ones have been known to be notorious for doing this to engines. hope you get it fixed man!
    ROTARYENGINEPETE
    '07 GMC SIERRA SLT | Z71 | 4X4 | 5.3L FF

    LIFT:
    ROUGH COUNTRY 3" PREMIUM SUSPENSION LIFT + ADD-A-LEAF
    18" ATX THUG WHEELS
    33" NITTO TRAIL GRAPPLER TIRES
    EBC SPORT ROTORS
    EBC YELLOW STUFF BRAKE PADS
    LIGHTING:
    HELLA/VVME 4300K HID LOW BEAMS

    HELLA BLACK MAGIC OFFROAD LIGHTS
    ANZO USA PROJECTORS HEADLIGHTS
    ANZO USA LED TAIL LIGHTS
    ENGINE:
    K&N 63 SERIES INTAKE
    MAGNAFLOW CATBACK D.O.S.I.F.T. EXHAUST
    BULLYDOG TRIPLE DOG GT TUNER

    PULSTAR IGNITORS
    OPTIMA RED TOP
    DRIVETRAIN:
    YUKON 4.56 GEARS
    MAG-HYTEC DIFF COVER
    CORVETTE SERVO
    TRANSGO SHIFT KIT
    Z-PACK 3-4 CLUTCH
    REBUILT WARN XFER CASE
    BODY:
    RUNCOOL HOOD LOUVERS
    FULL WEATHERTECH VISORS/BUGSHIELDS
    DUPONT BEDLINER

    DEEZEE BLACK DIAMOND PLATE BED CAPS
    BULLDOG LOCKING SPORT FUEL DOOR
    DOOR MOLDINGS REMOVED
    CUSTOM WIRE MESH GRILL
    BUSHWACKER BOSS FENDER FLARES
    CB THRU GLASS RADIO ANTENNA

    5.5sec 0-60mph on pavement (5.2sec running E85), and a little less in 3 feet of muddy water

  6. #16

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    carbon build up is a mpg killer too, this is so easy that if it fixes it u will throw urself off the cliff. get some B-12 Carb and Choke Cleaner, Throttle Body Cleaner, same thing best i can tell. soke the TB down with it and watch it melt, open it up and spray down in intake real good. spray in direction of runners for best results. now start it up and let it burn that out, then with it at idle start spraying it into the throttle body again and keep it running and keep spraying. for bad cases u may have to do the step where its not running and spraying it down the runners again. then keep it running spray heavily as u can into the intake.

  7. #17
    Legend

    Join Date
    Feb 2008
    Location
    Red Wing, Minnesota, United States
    Posts
    3,389

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    I wouldnt worry about the tire size, yeah it will effect it slightly but if its still dropping that isnt the proble, your stock tire was 29,5 and your new size is 31.6 inches tall, like i said it will effect it but that is neglagable, were you getting the 20+ with the bigger tires before. You could just buy a hypertech programmer so that you can put in the correct tire size
    99 K1500 Suburban LT "THE BEAST"
    Hypertech III, K&N, true dual
    285/75/16
    ___________________________
    Jason

  8. #18

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    I have had two trucks with the 4.3 in them one was a full size GMC and the other was a S10, i ran a glass pack in both of them and never had a issue with not enough back pressure. Tire size is a big factor in calculating gas mileage because it throws off your speedometer and your odometer as well. You could be getting a lot better gas mileage but because you are actually going farther than you truck thinks it is throwing you off. If you have a GPS like a Tom Tom or a Garmin i would try tracking your mileage through that and than compare it to what your trip meter says on the truck, and calculate your gas mileage using the GPS. You can also use the GPS to see how far off your speedometer is on your truck. On my truck i am running 35s and when my speedometer says 40 i am actually going 46, at 50 i am going 58. It is worth a try before you spend a bunch of money on a programmer or any more parts. These are just some ideas to try, im not sure if this is something you have already done but im just throwing them out there for ya, i hope they can help.

  9. #19

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    I matched the Tripometer with the Odometer on several trips where I knew the exact milage. I have the factory tire size back on the truck and around the cities here we have signs that say "Your speed" and show what your current speed is and they match. I don't know what to do anymore. I will try to clean the TB and see if that helps.

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